Speeding up build on autofoo projects

First of all, a little digression about build systems.

I’d like to clarify that I’m no lover of autotools. But I’m no lover of
any other build system, neither, and autotools is used on several open
source projects, including most of the ones I participate. It’s easily
copied and pasted by new projects. It’s known by distro maintainers how
to hack on it to work on different scenarios like cross-compilation,
distribute build across machines, different compilers, rpath, etc etc.
Moreover, from my experience, project maintainers usually dislike
changing the build system because it causes several …