phpBB has a custom kind of messy build system. I'm not sure if phing is the best solution, but recently came across it. It's worth considering.
Phing is based on apache's ant. It is a build system that is based on XML files. It's available through the third party PEAR channel and has good integration with PHPUnit. After installing the necessary dependencies, it's really easy to use.
I have seen it being used by doctrine 2, so that's a good reference implementation. Note: In case of doctrine this additional external package was required, and there may be an error message after running tests because the switch to git has not been fully completed yet.
