Fix gcc issue after install xcode 4.2
I can not install gem after installed xcode 4.2. It throws bus error.
the problem is xcode replace gcc with llvm-gcc
How to fix it:
1. Install standalone gcc
http://cloud.github.com/downloads/kennethreitz/osx-gcc-installer/GCC-10.7-v2.pkg
2. add gcc environment in your bash
export CC=/usr/bin/gcc-4.2
