ruby 1.9.2 with non-LLVM GCC

If you are having trouble installing ruby 1.9.2 and are seeing the following message:

Building 'ruby-1.9.2-p320' using clang - but it's not (fully) supported, expect errors.

Install ruby-1.9.2-p320 with gcc.

brew tap homebrew/dupes
brew install apple-gcc42
rvm reinstall 1.9.2 --with-gcc=gcc-4.2