+   # 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