title: Tool for debugging makefiles
body: <p>I have a large legacy codebase with very complicated makefiles, with lots of variables.  Sometimes I need to change them, and I find that it's very difficult to figure out why the change isn't working the way I expect.  What I'd like to find is a tool that basically does step-through-debugging of the "make" process, where I would give it a directory, and I would be able to see the value of different variables at different points in the process.  None of the debug flags to make seem to show me what I want, although it's possible that I'm missing something.  Does anyone know of a way to do this?</p>