Get Mountain Lion and Homebrew to Be Happy
1) Install XCode 4.4 into /Applications
Get it from the App Store.
2) Install Command Line Tools
In XCode's Preferences > Downloads you can install command line tools.
3) Let Everyone Know Where XCode Is
sudo xcode-select -switch /Applications/Xcode.app/Contents/Developer
4) Install X11
Visit http://xquartz.macosforge.org/trac/wiki and download and install 2.7.2+.
You will need to fix the symlink it makes:
ln -s /opt/X11 /usr/X11
5) Reinstall your brews
Will tell you what you need to check. Try out everything one by one and when one doesn't work
brew remove it and then reinstall it. If the install doesn't work, try
brew install it --use-gcc to prevent llvm from getting in the way.
Things that gave me issues that I had to remove and install:
You might need to install libxml2 and link it manually to make sure you don't get the wrong xml2-config if your path:
brew install libxml2 brew link libxml2
brew doctor and fix anything it tells you.
You may also need to symlink gcc for certain ruby gems and other stuff like that:
sudo ln -s /usr/bin/gcc /usr/bin/gcc-4.2
You are good to go.