Instalé gcc a través de homebrew sin errores.
brew install homebrew/versions/gcc49
brew unlink gcc49 && brew link gcc49
Pero cuando intento ejecutar gcc, se usa clang en su lugar.
~$:gcc --version
Configured with: --prefix=/Applications/Xcode.app/Contents/Developer/usr --with-gxx-include-dir=/usr/include/c++/4.2.1
Apple LLVM version 7.0.0 (clang-700.1.76)
Target: x86_64-apple-darwin15.0.0
Thread model: posix
Editar:
~$:type gcc
gcc is /usr/bin/gcc
~$:type /usr/bin/gcc
/usr/bin/gcc is /usr/bin/gcc
~$:echo $PATH
/usr/local/sbin:/Library/Frameworks/Python.framework/Versions/3.5/bin:/usr/local/bin:/usr/bin:/bin:/usr/sbin:/sbin:/Library/TeX/texbin