+ # If one of the targets is to build, force "clean" beforehand and disallow parallel build
+ ifneq ($(findstring all, $(MAKECMDGOALS)),)
+ MAKECMDGOALS := clean $(MAKECMDGOALS)
+ .NOTPARALLEL:
+ endif
+endif
+
+%: $(PROJECT_DIRECTORIES)
+ @echo . > /dev/null
+
+$(PROJECT_DIRECTORIES):
+ @$(MAKE) -C $@ $(MAKECMDGOALS)
+
+.PHONY: $(PROJECT_DIRECTORIES)