To compile Colobot on MacOS X, you need to first get Developer Command Line Tools for OS X, which you can get for example from [Apple Developer website](https://developer.apple.com/xcode/downloads/).
After installing Developer Command Line Tools, you should have basic tools like clang and git installed. After that, you can grab other required packages with Homebrew. So as in instructions on [the project page](http://brew.sh/):