Setting up an OS X build environment takes literally days of work for calibre. If you want to build calibre from source, run linux. I have absolutely zero interest in documenting build procedures for platforms that go out of their way to make building things difficult.
CALIBRE_DEVELOP_FROM provides a zero friction method of running calibre from source. Use it.
@fab672000: You do not need calibre-debug, as long as you have correctly set CALIBRE_DEVELOP_FROM, you can just run calibre normally. But if you do want it, on OS X, you need to install the command line tools via Preferences->Miscellaneous. A step that is clearly stated in the docs:
http://manual.calibre-ebook.com/deve...nt-environment
@KevinH: The provided sources are fully buildable if you know a lot about the OS and python and a couple of dozen other things and are willing to to spend a couple of days doing it.