One thing to point out specifically about "proper" Makefiles: the author should be marking his `.PHONY` targets (https://www.gnu.org/software/make/manual/html_node/Phony-Tar...) and giving sources. This gives you incremental builds for free.

One of my Makefiles: https://github.com/liveplant/liveplant-server/blob/master/Ma...

Definitely open to feedback on the above. Seems like my Makefile doing pretty much the same thing as yours @rcarmo.