Revert commit c90c7a33f5

targets.mk: Revert to cleanup at every compile for 'standard' targets.

Note: You can do 'dirty' builds with 'make compile-dirty' and 'make
test-dirty'.
- Disadvantage: these builds may fail due to the missing clean.
- Advantage: typically the 'dirty' builds are much faster.

mk/targets.mk

@@ -88,6 +88,8 @@ local.mk:
 	$(info ======================================================)
 	-@$(MAKE_LOCAL_MK)
 
+all compile::
+	$(foreach dir, doc lisp, $(MAKE) -C $(dir) clean;)
 compile compile-dirty::
 	$(MAKE) -C lisp $@
 all clean-install::