Merge branch 'mk/make-rm-depdirs-could-be-empty'

"make COMPUTE_HEADER_DEPENDENCIES=no clean" would try to run "rm
-rf $(dep_dirs)" with an empty dep_dir, but some implementations of
"rm -rf" barf on an empty argument list.

* mk/make-rm-depdirs-could-be-empty:
  Makefile: don't run "rm" without any files

Makefile

@@ -2449,8 +2449,7 @@ clean: profile-clean
 		builtin/*.o $(LIB_FILE) $(XDIFF_LIB) $(VCSSVN_LIB)
 	$(RM) $(ALL_PROGRAMS) $(SCRIPT_LIB) $(BUILT_INS) git$X
 	$(RM) $(TEST_PROGRAMS)
-	$(RM) -r bin-wrappers
-	$(RM) -r $(dep_dirs)
+	$(RM) -r bin-wrappers $(dep_dirs)
 	$(RM) -r po/build/
 	$(RM) *.spec *.pyc *.pyo */*.pyc */*.pyo common-cmds.h $(ETAGS_TARGET) tags cscope*
 	$(RM) -r $(GIT_TARNAME) .doc-tmp-dir