1 make: "directive-ifmake.mk" line 8: ok: positive condition works
2 make: "directive-ifmake.mk" line 19: ok: negation works
3 make: "directive-ifmake.mk" line 25: ok: double negation works
4 make: "directive-ifmake.mk" line 32: ok: both mentioned
5 make: "directive-ifmake.mk" line 39: ok: only those mentioned
6 make: "directive-ifmake.mk" line 49: Targets can even be added at parse time.