ERROR: The provided CC(gcc) is LLVM based, it is not yet fully supported by ruby and gems, please read `rvm requirements`.
1) Download Xcode 4.2.x via App Store.
2) Go to Applications folder and click Install Xcode
3) Download and install GCC from https://github.com/kennethreitz/osx-gcc-installer
4) In a new terminal run : export CC=gcc
and then run : rvm install 1.9.3
5) You may also want to upgrade ruby gems by running:
gem update --system