Install Ruby Enterprise Edition with Homebrew on Mountain Lion (Mac OS X 10.8.3)

session.sh

> brew install ruby-enterprise-edition --use-gcc
==> Downloading http://rubyenterpriseedition.googlecode.com/files/ruby-enterprise-1.8.7-2011.03.tar.gz
Already downloaded: /Library/Caches/Homebrew/ruby-enterprise-edition-2011.03.tar.gz
==> ./installer --auto /usr/local/Cellar/ruby-enterprise-edition/2011.03 --no-tcmalloc -c --with-readline-dir=/usr/local/Cellar/readline/6.2.4
==> Caveats
By default we don't compile REE as a shared library. From their documentation:
    Please note that enabling --enable-shared will make the Ruby interpreter
    about 20% slower.

For desktop environments (particularly ones requiring RubyCocoa) this is
acceptable and even desirable.

If you need REE to be compiled as a shared library, you can re-compile like so:
    brew install ruby-enterprise-edition --force --enable-shared
Warning: Could not link ruby-enterprise-edition. Unlinking...
Error: The `brew link` step did not complete successfully
The formula built, but is not symlinked into /usr/local
You can try again using `brew link ruby-enterprise-edition'
==> Summary
??  /usr/local/Cellar/ruby-enterprise-edition/2011.03: 7501 files, 73M, built in 2.9 minutes
> brew link --overwrite ruby-enterprise-edition                                                                                                                                                    10:40:55
Linking /usr/local/Cellar/ruby-enterprise-edition/2011.03... 31 symlinks created
> ruby -v
ruby 1.8.7 (2011-02-18 patchlevel 334) [i686-darwin12.3.0], MBARI 0x6770, Ruby Enterprise Edition 2011.03
> brew link --overwrite ruby
Linking /usr/local/Cellar/ruby/2.0.0-p0... 34 symlinks created
> ruby -v
ruby 2.0.0p0 (2013-02-24 revision 39474) [x86_64-darwin12.3.0]
> brew link --overwrite ruby-enterprise-edition
Linking /usr/local/Cellar/ruby-enterprise-edition/2011.03... 31 symlinks created
> ruby -v
ruby 1.8.7 (2011-02-18 patchlevel 334) [i686-darwin12.3.0], MBARI 0x6770, Ruby Enterprise Edition 2011.03

For some reason, setting CC=gcc or the like did not work on my machine. I tried a lot of different things, but finally discovered that Homebrew's '--use-gcc' flag did the trick properly.