The macOS version of GNU Make is stuck at 3.81, which I discovered does not print the information needed by vim's quickfix feature when traversing subdirectories using `make -C`. Installing the latest version of GNU Make (4.4) using `brew install make` fixed that problem.
The frozen macOS build also has some weird issue with my makefiles where it sometimes finishes the job but then sits there spinning at 100% CPU forever :(.