-ifneq ($(MAKECMDGOALS),tools-only)
-DIRS += runtime docs
-OPTIONAL_DIRS = examples projects
+ifeq ($(MAKECMDGOALS),tools-only)
+DIRS += tools
+else
+ ifneq ($(MAKECMDGOALS),libs-only)
+ DIRS += tools runtime docs
+ OPTIONAL_DIRS = examples projects
+ endif