May projects use some document generators or tools to collect metrics. However some build-systems that were really interesting were OpenCV and OpenSSL.

OpenSSL buildsystem is over 6k lines of perl scripts which communicate over pipes.

OpenCV uses cmake, python and prolog for it's build. Until this day, I have no clue why there is prolog involved.

You can read some bits about it in our initial announcement of buildinfer: https://hackernoon.com/announcing-buildinfer-for-c-3dfa3eb15...