Configurando MRI 1.9.3 no OSX Lion

Primeiro desinstale o Xcode:

$ sudo /Developer/Library/uninstall-devtools --mode=all 

Baixe as ferramentas de linha de comando oficiais da Apple: https://daw.apple.com/cgi-bin/WebObjects/DSAuthWeb.woa/wa/login?appIdKey=d4f7d769c2abecc664d0dadfed6a67f943442b5e9c87524d4587a95773750cea%5Fownload2Fownload2Fownload

$ brew update
$ brew install autoconf automake

$ brew install https
://raw.github.com/Homebrew/homebrew-dupes/master/apple-gcc42.rb
$ rvm
get head
$ rvm install
1.9.3-head