brew install gcc; sudo mv /usr/bin/gcc /usr/bin/gcc_org; sudo ln -s /usr/local/bin/gcc-4.7 /usr/bin/gcc; rvm reinstall 1.9.3

brew install gcc;
sudo mv /usr/bin/gcc /usr/bin/gcc_org;
sudo ln -s /usr/local/bin/gcc-4.7 /usr/bin/gcc;
rvm reinstall 1.9.3