Somehow rails stopped working so I was trying to reinstall it, but I got this error:

ERROR: The provided CC(/usr/bin/gcc) is LLVM based, it is not yet fully supported by ruby and gems, please read rvm requirements.

Found this post: http://stackoverflow.com/questions/8000145/ruby-rvm-llvm-and-mysql

Did

rvm get head

rvm install

That fixed my problem