Update to reflect KKWT's graduation to API 20.

Change-Id: I4716e71d72b2526fe635079d1b15f623db842c21
diff --git a/CleanSpec.mk b/CleanSpec.mk
index 86c555b..ca37637 100644
--- a/CleanSpec.mk
+++ b/CleanSpec.mk
@@ -255,6 +255,11 @@
 # Switching PRODUCT_RUNTIMES default for some devices
 $(call add-clean-step, rm -rf $(PRODUCT_OUT)/system/build.prop)
 
+# KKWT has become API 20
+$(call add-clean-step, rm -rf $(PRODUCT_OUT)/system/build.prop)
+$(call add-clean-step, rm -rf $(PRODUCT_OUT)/system/app/*)
+$(call add-clean-step, rm -rf $(PRODUCT_OUT)/obj/APPS/*)
+
 # ************************************************
 # NEWER CLEAN STEPS MUST BE AT THE END OF THE LIST
 # ************************************************