If anyone wants to do non-recursive make for big projects, I would take a look at what the Android platform does. They have this elaborate Android.mk makefile fragment system.
At the beginning of the build you go and find all the fragments, then process/concatenate them into one huge makefile, and do a single make invocation. It results in a very parallelizable build.
It seems kinda crazy and hacky but it definitely works better than recursive make.
For some reason the best docs seem to be on this Korean site: