make: "cond-op-not.mk" line 30: Not empty evaluates to true.
make: "cond-op-not.mk" line 39: Not space evaluates to false.
make: "cond-op-not.mk" line 44: Not 0 evaluates to true.
make: "cond-op-not.mk" line 53: Not 1 evaluates to false.
make: "cond-op-not.mk" line 60: Not word evaluates to false.
make: "cond-op-not.mk" line 65: Malformed conditional '!'
make: Fatal errors encountered -- cannot continue
make: stopped making "all" in unit-tests
exit status 1