How to install proj4rb on Ubuntu 14.04?

I am trying to install proj4rb on Ubuntu 14.04. Three methods are provided in the README file, but they all fail.

1. Using gem

$ gem install proj4rb
Building native extensions.  This could take a while...
ERROR:  Error installing proj4rb:
    ERROR: Failed to build gem native extension.

    /home/desousa/.rvm/gems/ruby-1.9.2-p290 extconf.rb
checking for proj_api.h... yes
checking for projects.h... yes
checking for pj_init() in -lproj... yes
creating Makefile

make "DESTDIR="
linking shared-object proj4_ruby.so
projrb.o: In function `proj_get_def':
c:\mingw64\mingw64\local\src\proj4rb\ext/projrb.c:146: undefined reference to `rb_check_type'
c:\mingw64\mingw64\local\src\proj4rb\ext/projrb.c:147: undefined reference to `pj_get_def'
projrb.o: In function `proj_is_geocent':
c:\mingw64\mingw64\local\src\proj4rb\ext/projrb.c:135: undefined reference to `rb_check_type'
c:\mingw64\mingw64\local\src\proj4rb\ext/projrb.c:136: undefined reference to `pj_is_geocent'
projrb.o: In function `proj_is_latlong':
c:\mingw64\mingw64\local\src\proj4rb\ext/projrb.c:124: undefined reference to `rb_check_type'
c:\mingw64\mingw64\local\src\proj4rb\ext/projrb.c:125: undefined reference to `pj_is_latlong'
projrb.o: In function `proj_initialize':
c:\mingw64\mingw64\local\src\proj4rb\ext/projrb.c:79: undefined reference to `rb_funcall'
c:\mingw64\mingw64\local\src\proj4rb\ext/projrb.c:86: undefined reference to `rb_ary_entry'
c:\mingw64\mingw64\local\src\proj4rb\ext/projrb.c:87: undefined reference to `rb_string_value_ptr'
c:\mingw64\mingw64\local\src\proj4rb\ext/projrb.c:90: undefined reference to `rb_check_type'
c:\mingw64\mingw64\local\src\proj4rb\ext/projrb.c:91: undefined reference to `pj_init'
c:\mingw64\mingw64\local\src\proj4rb\ext/projrb.c:94: undefined reference to `pj_get_errno_ref'
projrb.o: In function `raise_error':
c:\mingw64\mingw64\local\src\proj4rb\ext/projrb.c:35: undefined reference to `rb_funcall'
projrb.o: In function `rb_int2num_inline':
c:\mingw64\mingw64\local\src\proj4rb\ext/c:/mingw64/mingw64/local/ruby/include/ruby-2.1.0/ruby/ruby.h:1286: undefined reference to `rb_int2big'
projrb.o: In function `proj_initialize':
c:\mingw64\mingw64\local\src\proj4rb\ext/projrb.c:96: undefined reference to `rb_raise'
projrb.o: In function `proj_free':
c:\mingw64\mingw64\local\src\proj4rb\ext/projrb.c:41: undefined reference to `pj_free'
projrb.o: In function `proj_error_message':
c:\mingw64\mingw64\local\src\proj4rb\ext/projrb.c:62: undefined reference to `pj_strerrno'
projrb.o: In function `rb_num2long_inline':
c:\mingw64\mingw64\local\src\proj4rb\ext/c:/mingw64/mingw64/local/ruby/include/ruby-2.1.0/ruby/ruby.h:598: undefined reference to `rb_num2long'
projrb.o: In function `proj_error_message':
c:\mingw64\mingw64\local\src\proj4rb\ext/projrb.c:62: undefined reference to `pj_strerrno'
projrb.o: In function `proj_forward':
c:\mingw64\mingw64\local\src\proj4rb\ext/projrb.c:161: undefined reference to `rb_check_type'
c:\mingw64\mingw64\local\src\proj4rb\ext/projrb.c:163: undefined reference to `rb_funcall'
c:\mingw64\mingw64\local\src\proj4rb\ext/projrb.c:163: undefined reference to `rb_num2dbl'
c:\mingw64\mingw64\local\src\proj4rb\ext/projrb.c:164: undefined reference to `rb_funcall'
c:\mingw64\mingw64\local\src\proj4rb\ext/projrb.c:164: undefined reference to `rb_num2dbl'
c:\mingw64\mingw64\local\src\proj4rb\ext/projrb.c:165: undefined reference to `pj_fwd'
c:\mingw64\mingw64\local\src\proj4rb\ext/projrb.c:167: undefined reference to `pj_get_errno_ref'
projrb.o: In function `raise_error':
c:\mingw64\mingw64\local\src\proj4rb\ext/projrb.c:35: undefined reference to `rb_funcall'
projrb.o: In function `proj_forward':
c:\mingw64\mingw64\local\src\proj4rb\ext/projrb.c:169: undefined reference to `rb_float_new'
c:\mingw64\mingw64\local\src\proj4rb\ext/projrb.c:169: undefined reference to `rb_funcall'
c:\mingw64\mingw64\local\src\proj4rb\ext/projrb.c:170: undefined reference to `rb_float_new'
c:\mingw64\mingw64\local\src\proj4rb\ext/projrb.c:170: undefined reference to `rb_funcall'
projrb.o: In function `raise_error':
c:\mingw64\mingw64\local\src\proj4rb\ext/c:/mingw64/mingw64/local/ruby/include/ruby-2.1.0/ruby/ruby.h:1286: undefined reference to `rb_int2big'
projrb.o: In function `proj_forward':
c:\mingw64\mingw64\local\src\proj4rb\ext/projrb.c:173: undefined reference to `rb_raise'
projrb.o: In function `proj_inverse':
c:\mingw64\mingw64\local\src\proj4rb\ext/projrb.c:192: undefined reference to `rb_check_type'
c:\mingw64\mingw64\local\src\proj4rb\ext/projrb.c:194: undefined reference to `rb_funcall'
c:\mingw64\mingw64\local\src\proj4rb\ext/projrb.c:194: undefined reference to `rb_num2dbl'
c:\mingw64\mingw64\local\src\proj4rb\ext/projrb.c:195: undefined reference to `rb_funcall'
c:\mingw64\mingw64\local\src\proj4rb\ext/projrb.c:195: undefined reference to `rb_num2dbl'
c:\mingw64\mingw64\local\src\proj4rb\ext/projrb.c:196: undefined reference to `pj_inv'
c:\mingw64\mingw64\local\src\proj4rb\ext/projrb.c:198: undefined reference to `pj_get_errno_ref'
projrb.o: In function `raise_error':
c:\mingw64\mingw64\local\src\proj4rb\ext/projrb.c:35: undefined reference to `rb_funcall'
projrb.o: In function `proj_inverse':
c:\mingw64\mingw64\local\src\proj4rb\ext/projrb.c:200: undefined reference to `rb_float_new'
c:\mingw64\mingw64\local\src\proj4rb\ext/projrb.c:200: undefined reference to `rb_funcall'
c:\mingw64\mingw64\local\src\proj4rb\ext/projrb.c:201: undefined reference to `rb_float_new'
c:\mingw64\mingw64\local\src\proj4rb\ext/projrb.c:201: undefined reference to `rb_funcall'
projrb.o: In function `raise_error':
c:\mingw64\mingw64\local\src\proj4rb\ext/c:/mingw64/mingw64/local/ruby/include/ruby-2.1.0/ruby/ruby.h:1286: undefined reference to `rb_int2big'
projrb.o: In function `proj_inverse':
c:\mingw64\mingw64\local\src\proj4rb\ext/projrb.c:204: undefined reference to `rb_raise'
projrb.o: In function `proj_transform':
c:\mingw64\mingw64\local\src\proj4rb\ext/projrb.c:229: undefined reference to `rb_check_type'
c:\mingw64\mingw64\local\src\proj4rb\ext/projrb.c:230: undefined reference to `rb_check_type'
c:\mingw64\mingw64\local\src\proj4rb\ext/projrb.c:232: undefined reference to `rb_funcall'
c:\mingw64\mingw64\local\src\proj4rb\ext/projrb.c:232: undefined reference to `rb_num2dbl'
c:\mingw64\mingw64\local\src\proj4rb\ext/projrb.c:233: undefined reference to `rb_funcall'
c:\mingw64\mingw64\local\src\proj4rb\ext/projrb.c:233: undefined reference to `rb_num2dbl'
c:\mingw64\mingw64\local\src\proj4rb\ext/projrb.c:236: undefined reference to `rb_respond_to'
c:\mingw64\mingw64\local\src\proj4rb\ext/projrb.c:242: undefined reference to `pj_transform'
projrb.o: In function `raise_error':
c:\mingw64\mingw64\local\src\proj4rb\ext/projrb.c:35: undefined reference to `rb_funcall'
projrb.o: In function `proj_transform':
c:\mingw64\mingw64\local\src\proj4rb\ext/projrb.c:237: undefined reference to `rb_funcall'
c:\mingw64\mingw64\local\src\proj4rb\ext/projrb.c:237: undefined reference to `rb_num2dbl'
c:\mingw64\mingw64\local\src\proj4rb\ext/projrb.c:244: undefined reference to `rb_float_new'
c:\mingw64\mingw64\local\src\proj4rb\ext/projrb.c:244: undefined reference to `rb_funcall'
c:\mingw64\mingw64\local\src\proj4rb\ext/projrb.c:245: undefined reference to `rb_float_new'
c:\mingw64\mingw64\local\src\proj4rb\ext/projrb.c:245: undefined reference to `rb_funcall'
c:\mingw64\mingw64\local\src\proj4rb\ext/projrb.c:247: undefined reference to `rb_respond_to'
c:\mingw64\mingw64\local\src\proj4rb\ext/projrb.c:248: undefined reference to `rb_float_new'
c:\mingw64\mingw64\local\src\proj4rb\ext/projrb.c:248: undefined reference to `rb_funcall'
projrb.o: In function `raise_error':
c:\mingw64\mingw64\local\src\proj4rb\ext/c:/mingw64/mingw64/local/ruby/include/ruby-2.1.0/ruby/ruby.h:1286: undefined reference to `rb_int2big'
projrb.o: In function `proj_transform':
c:\mingw64\mingw64\local\src\proj4rb\ext/projrb.c:252: undefined reference to `rb_raise'
projrb.o: In function `Init_proj4_ruby':
c:\mingw64\mingw64\local\src\proj4rb\ext/projrb.c:494: undefined reference to `rb_intern2'
c:\mingw64\mingw64\local\src\proj4rb\ext/projrb.c:496: undefined reference to `rb_define_module'
c:\mingw64\mingw64\local\src\proj4rb\ext/projrb.c:501: undefined reference to `rb_float_new'
c:\mingw64\mingw64\local\src\proj4rb\ext/projrb.c:501: undefined reference to `rb_define_const'
c:\mingw64\mingw64\local\src\proj4rb\ext/projrb.c:505: undefined reference to `rb_float_new'
c:\mingw64\mingw64\local\src\proj4rb\ext/projrb.c:505: undefined reference to `rb_define_const'
c:\mingw64\mingw64\local\src\proj4rb\ext/projrb.c:509: undefined reference to `rb_float_new'
c:\mingw64\mingw64\local\src\proj4rb\ext/projrb.c:509: undefined reference to `rb_define_const'
c:\mingw64\mingw64\local\src\proj4rb\ext/projrb.c:511: undefined reference to `rb_path2class'
c:\mingw64\mingw64\local\src\proj4rb\ext/projrb.c:511: undefined reference to `rb_define_class_under'
c:\mingw64\mingw64\local\src\proj4rb\ext/projrb.c:512: undefined reference to `rb_define_singleton_method'
c:\mingw64\mingw64\local\src\proj4rb\ext/projrb.c:514: undefined reference to `rb_define_class_under'
c:\mingw64\mingw64\local\src\proj4rb\ext/projrb.c:515: undefined reference to `rb_define_alloc_func'
c:\mingw64\mingw64\local\src\proj4rb\ext/projrb.c:516: undefined reference to `rb_define_method'
c:\mingw64\mingw64\local\src\proj4rb\ext/projrb.c:520: undefined reference to `rb_define_method'
c:\mingw64\mingw64\local\src\proj4rb\ext/projrb.c:521: undefined reference to `rb_define_method'
c:\mingw64\mingw64\local\src\proj4rb\ext/projrb.c:522: undefined reference to `rb_define_alias'
c:\mingw64\mingw64\local\src\proj4rb\ext/projrb.c:523: undefined reference to `rb_define_method'
c:\mingw64\mingw64\local\src\proj4rb\ext/projrb.c:524: undefined reference to `rb_define_method'
c:\mingw64\mingw64\local\src\proj4rb\ext/projrb.c:525: undefined reference to `rb_define_method'
c:\mingw64\mingw64\local\src\proj4rb\ext/projrb.c:493: undefined reference to `rb_intern2'
c:\mingw64\mingw64\local\src\proj4rb\ext/projrb.c:492: undefined reference to `rb_intern2'
c:\mingw64\mingw64\local\src\proj4rb\ext/projrb.c:491: undefined reference to `rb_intern2'
c:\mingw64\mingw64\local\src\proj4rb\ext/projrb.c:490: undefined reference to `rb_intern2'
c:\mingw64\mingw64\local\src\proj4rb\ext/projrb.c:489: undefined reference to `rb_intern2'
projrb.o:c:\mingw64\mingw64\local\src\proj4rb\ext/projrb.c:488: more undefined references to `rb_intern2' follow
projrb.o: In function `proj_get_def':
c:\mingw64\mingw64\local\src\proj4rb\ext/projrb.c:147: undefined reference to `rb_str_new_cstr'
projrb.o: In function `proj_alloc':
c:\mingw64\mingw64\local\src\proj4rb\ext/projrb.c:50: undefined reference to `rb_data_object_alloc'
projrb.o: In function `proj_error_message':
c:\mingw64\mingw64\local\src\proj4rb\ext/projrb.c:64: undefined reference to `rb_str_new_cstr'
c:\mingw64\mingw64\local\src\proj4rb\ext/projrb.c:66: undefined reference to `rb_str_new'
projrb.o: In function `Init_proj4_ruby':
c:\mingw64\mingw64\local\src\proj4rb\ext/projrb.c:526: undefined reference to `rb_define_method'
projrb.o:projrb.c:(.rdata$.refptr.rb_cObject[.refptr.rb_cObject]+0x0): undefined reference to `rb_cObject'
projrb.o:projrb.c:(.rdata$.refptr.rb_eSystemCallError[.refptr.rb_eSystemCallError]+0x0): undefined reference to `rb_eSystemCallError'
collect2: error: ld returned 1 exit status
make: *** [proj4_ruby.so] Error 1

Gem files will remain installed in /home/desousa/.rvm/gems/ruby-1.9.2-p290/gems/proj4rb-1.0.0 for inspection.
Results logged to /home/desousa/.rvm/gems/ruby-1.9.2-p290/extensions/x86_64-linux/1.9.1/proj4rb-1.0.0/gem_make.out

There is an open issue at GitHub with this problem.

2. Using rake

$ cd ~/temp/ruby/proj4rb-1.0.0
$ ls -la
total 56
drwx------ 7 desousa desousa 4096 Feb 24 09:59 .
drwxrwxr-x 3 desousa desousa 4096 Feb 24 10:00 ..
-rw-rw-r-- 1 desousa desousa 1050 Dec 15 04:13 ChangeLog
drwx------ 2 desousa desousa 4096 Feb 24 09:59 data
drwx------ 2 desousa desousa 4096 Feb 24 09:59 example
drwx------ 3 desousa desousa 4096 Feb 24 09:59 ext
-rw-rw-r-- 1 desousa desousa   86 Dec 15 04:13 .gitignore
drwx------ 2 desousa desousa 4096 Feb 24 09:59 lib
-rw-rw-r-- 1 desousa desousa 1130 Dec 15 04:13 MIT-LICENSE
-rw-rw-r-- 1 desousa desousa 1068 Dec 15 04:13 proj4rb.gemspec
-rw-rw-r-- 1 desousa desousa 1020 Dec 15 04:13 Rakefile
-rw-rw-r-- 1 desousa desousa 6211 Dec 15 04:13 README.rdoc
drwx------ 2 desousa desousa 4096 Feb 24 09:59 test

$ rake build --trace
rake aborted!
Don't know how to build task 'build'
/home/desousa/.rvm/gems/ruby-1.9.2-p290/gems/rake-10.3.2/lib/rake/task_manager.rb:62:in `[]'
/home/desousa/.rvm/gems/ruby-1.9.2-p290/gems/rake-10.3.2/lib/rake/application.rb:149:in `invoke_task'
/home/desousa/.rvm/gems/ruby-1.9.2-p290/gems/rake-10.3.2/lib/rake/application.rb:106:in `block (2 levels) in top_level'
/home/desousa/.rvm/gems/ruby-1.9.2-p290/gems/rake-10.3.2/lib/rake/application.rb:106:in `each'
/home/desousa/.rvm/gems/ruby-1.9.2-p290/gems/rake-10.3.2/lib/rake/application.rb:106:in `block in top_level'
/home/desousa/.rvm/gems/ruby-1.9.2-p290/gems/rake-10.3.2/lib/rake/application.rb:115:in `run_with_threads'
/home/desousa/.rvm/gems/ruby-1.9.2-p290/gems/rake-10.3.2/lib/rake/application.rb:100:in `top_level'
/home/desousa/.rvm/gems/ruby-1.9.2-p290/gems/rake-10.3.2/lib/rake/application.rb:78:in `block in run'
/home/desousa/.rvm/gems/ruby-1.9.2-p290/gems/rake-10.3.2/lib/rake/application.rb:176:in `standard_exception_handling'
/home/desousa/.rvm/gems/ruby-1.9.2-p290/gems/rake-10.3.2/lib/rake/application.rb:75:in `run'
/home/desousa/.rvm/gems/ruby-1.9.2-p290/gems/rake-10.3.2/bin/rake:33:in `<top (required)>'
/home/desousa/.rvm/gems/ruby-1.9.2-p290/bin/rake:23:in `load'
/home/desousa/.rvm/gems/ruby-1.9.2-p290/bin/rake:23:in `<main>'

3. Using make

$ cd ext
$ ruby extconf.rb
checking for proj_api.h... yes
checking for projects.h... yes
checking for pj_init() in -lproj... yes
creating Makefile
$ make
gcc -I. -I/home/desousa/.rvm/rubies/ruby-1.9.2-p290/include/ruby-1.9.1/x86_64-linux -I/home/desousa/.rvm/rubies/ruby-1.9.2-p290/include/ruby-1.9.1/ruby/backward -I/home/desousa/.rvm/rubies/ruby-1.9.2-p290/include/ruby-1.9.1 -I. -DHAVE_PROJ_API_H -DHAVE_PROJECTS_H    -fPIC -O3 -ggdb -Wextra -Wno-unused-parameter -Wno-parentheses -Wpointer-arith -Wwrite-strings -Wno-missing-field-initializers -Wno-long-long  -fPIC  -o projrb.o -c projrb.c
In file included from /usr/local/include/projects.h:244:0,
                 from projrb.c:3:
/usr/include/proj_api.h:61:5: error: unknown type name ‘projCtx_t’
     typedef projCtx_t *projCtx;
     ^
make: *** [projrb.o] Error 1

Update I: I have tried to install proj4rb19, a version specifically targeted for Ruby 1.9. While it compiles correctly, it fails to install.

Update II: I am using RVM, with the following setup:

$ rvm -v
rvm 1.26.10 (manual) by Wayne E. Seguin <wayneeseguin@gmail.com>, Michal Papis <mpapis@gmail.com> [https://rvm.io/]
$ ruby -v
ruby 1.9.3p551 (2014-11-13 revision 48407) [x86_64-linux]
$ gem -v
2.4.3