Clean step for libc.

(cherry-pick of ab1e93d4d4f4a46fa922df5ba7ccd41dde1221ac.)

Change-Id: I304312d6eb0346c050d02bd834565e0d43d8b4dd
diff --git a/CleanSpec.mk b/CleanSpec.mk
index 6d81733..8109ebb 100644
--- a/CleanSpec.mk
+++ b/CleanSpec.mk
@@ -127,6 +127,11 @@
 
 $(call add-clean-step, rm -f $(OUT_DIR)/versions_checked.mk)
 
+$(call add-clean-step, rm -rf $(PRODUCT_OUT)/obj/STATIC_LIBRARIES)
+$(call add-clean-step, rm -rf $(PRODUCT_OUT)/obj/SHARED_LIBRARIES)
+$(call add-clean-step, rm -rf $(PRODUCT_OUT)/obj/EXECUTABLES)
+$(call add-clean-step, rm -rf $(PRODUCT_OUT)/obj/lib/*.o)
+
 # ************************************************
 # NEWER CLEAN STEPS MUST BE AT THE END OF THE LIST
 # ************************************************