Isn't suckless supposed to use a portable subset of Makefile that's understood by most make-programs? Relying on gmake is usually a bad idea, even if it's present everywhere. I try to keep my makefiles portable by - for instance - using
.c.o: <rule> instead of %.o: %.c <rule> which would be a GNU extension. Just sayin'. Writing portable makefiles is perfectly possible for our simple needs. (In my opinion, it's even possible for projects far larger than ours). Do yourself and us a favour and test your makefiles using bmake before deploying. Packages exist for $LINUX_DISTRO!