Fixing gcc on mountain lion for gem install

When you install Mountain Lion, you will no longer have build tools such as gcc or make

Step 1, get the latest Xcode, and install Command Line Tools, granting you make and gcc

Step 2, create the symlink so that your bundler/gem commands will locate gcc correctly : sudo ln -s /usr/bin/gcc /usr/bin/gcc-4.2

Step 3, done! You don’t need MacPorts or a special version of gcc, the one installed by Xcode4.5 Developer Preview 2 is just fine and compiles native extensions for me successfully.