Clean out *.prop files due to dex2oat instruction-set flag change.

Change-Id: Ib1e94cfe08bad9e51fd46e8a1a09926877f179de
diff --git a/CleanSpec.mk b/CleanSpec.mk
index 020de69..3e5d199 100644
--- a/CleanSpec.mk
+++ b/CleanSpec.mk
@@ -305,6 +305,11 @@
 # Move to libc++ as the default STL.
 $(call add-clean-step, rm -rf $(OUT_DIR))
 
+# dex2oat instruction-set changes
+$(call add-clean-step, rm -rf $(PRODUCT_OUT)/system/build.prop)
+$(call add-clean-step, rm -rf $(PRODUCT_OUT)/root/default.prop)
+$(call add-clean-step, rm -rf $(PRODUCT_OUT)/recovery/root/default.prop)
+
 # ************************************************
 # NEWER CLEAN STEPS MUST BE AT THE END OF THE LIST
 # ************************************************