rdiscount "ERROR: Failed to build gem native extension." - rvm

Question

This is interesting. I had rdiscount working within one rvm gemset, but when I tried to add it to another, I would get ERROR: Failed to build gem native extension. So I tried removing it from the original gemset and re-installing it only to get the same error. I'm not sure what is going on. I'm trying to use it with Jekyll and Octopress builds. I'm on OS X 10.7.5.
Here's what happens:
Using /Users/rachelnabors/.rvm/gems/ruby-1.9.2-p290 with gemset jekyll
Can-Opener:RachelNabors.com rachelnabors$ gem install rdiscount
Building native extensions. This could take a while...
ERROR: Error installing rdiscount:
ERROR: Failed to build gem native extension.
/Users/rachelnabors/.rvm/rubies/ruby-1.9.2-p290/bin/ruby extconf.rb
checking for random()... yes
checking for srandom()... yes
checking for rand()... yes
checking for srand()... yes
checking size of unsigned long... long
checking size of unsigned int... int
no int with size 4
*** extconf.rb failed ***
Could not create Makefile due to some reason, probably lack of
necessary libraries and/or headers. Check the mkmf.log file for more
details. You may need configuration options.
Provided configuration options:
--with-opt-dir
--without-opt-dir
--with-opt-include
--without-opt-include=${opt-dir}/include
--with-opt-lib
--without-opt-lib=${opt-dir}/lib
--with-make-prog
--without-make-prog
--srcdir=.
--curdir
--ruby=/Users/rachelnabors/.rvm/rubies/ruby-1.9.2-p290/bin/ruby
--with-rdiscount-dir
--without-rdiscount-dir
--with-rdiscount-include
--without-rdiscount-include=${rdiscount-dir}/include
--with-rdiscount-lib
--without-rdiscount-lib=${rdiscount-dir}/lib
Gem files will remain installed in /Users/rachelnabors/.rvm/gems/ruby-1.9.2-p290#jekyll/gems/rdiscount-2.0.7.1 for inspection.
Results logged to /Users/rachelnabors/.rvm/gems/ruby-1.9.2-p290#jekyll/gems/rdiscount-2.0.7.1/ext/gem_make.out

Answer 1

Same failure:
https://github.com/rtomayko/rdiscount/issues/48
Ruby 1.9.2 isn't supported. See also:
https://github.com/rtomayko/rdiscount/wiki/Support-Matrix
1.9.3 should do ya fine!