-# $(subdir-obj-y) is the list of objects in $(obj-y) which do not live
-# in the local directory
-subdir-obj-y := $(foreach o,$(obj-y),$(if $(filter-out $(o),$(notdir $(o))),$(o)))
+# $(subdir-obj-y) is the list of objects in $(obj-y) which uses dir/ to
+# tell kbuild to descend
+subdir-obj-y := $(filter %/built-in.o, $(obj-y))