This is a reference project that contains multiple libraries and programs which are all built with a single Make process. Each sub-Makefile is included in the top-level one, which has full knowledge of what is going on. For some history on this, read the 'Recursive Make Considered Harmful' paper - http://www.lateralt.net/files/auug97.pdf
- All builds must be executed from the top-level
- https://www.oreilly.com/library/view/managing-projects-with/0596006101/ch06.html
- https://mischasan.wordpress.com/2013/03/30/non-recursive-make-gmake-part-1-the-basic-gnumakefile-layouts/
- http://clarkgrubb.com/makefile-style-guide
- http://nuclear.mutantstargoat.com/articles/make/#automatic-include-dependency-tracking