No bug, if a tools directory fails to build it frequently doesn't stop the build like it should, missing EXIT_ON_ERROR

config/rules.mk

@@ -610,7 +610,8 @@ export:: $(SUBMAKEFILES) $(MAKE_DIRS)
 tools:: $(SUBMAKEFILES) $(MAKE_DIRS)
 	+$(LOOP_OVER_DIRS)
 ifdef TOOL_DIRS
-	@for d in $(TOOL_DIRS); do \
+	@$(EXIT_ON_ERROR) \
+	for d in $(TOOL_DIRS); do \
 	    $(UPDATE_TITLE) \
 	    $(MAKE) -C $$d libs; \
 	done