ENABLED = A B

# Helper function
unmet_requirements = $(filter-out $(ENABLED),$(REQUIRE))

%.exe :
	@echo Creating executable $@
	@touch $@

run% :
	@$(if $(unmet_requirements),echo "Skipping $@ due to unmet requirements:" $(unmet_requirements),echo Running $@)

runfoo1 : REQUIRE = A B
runfoo1 : foo.exe

runfoo2 : REQUIRE = A C
runfoo2 : foo.exe

runbar1 : REQUIRE = A
runbar1 : bar.exe

allrun : runfoo1 runfoo2 runbar1

.INTERMEDIATE: foo.exe bar.exe