Pass device characteristic information through to aapt.

A build configuration can define PRODUCT_CHARACTERISTICS, which is
a comma-separated list of device characteristics, for example
"nosdcard,grayscale".  This will be passed through to aapt with
the --product flag.

Change-Id: I902c034b2f2824dbd2d33449308ee08beeb09551
diff --git a/CleanSpec.mk b/CleanSpec.mk
index fc35169..2663780 100644
--- a/CleanSpec.mk
+++ b/CleanSpec.mk
@@ -50,6 +50,7 @@
 $(call add-clean-step, rm -rf $(PRODUCT_OUT)/system/build.prop)
 $(call add-clean-step, rm -rf $(PRODUCT_OUT)/system/vendor)
 $(call add-clean-step, rm -rf $(PRODUCT_OUT)/android-info.txt)
+$(call add-clean-step, find $(PRODUCT_OUT) -name "*.apk" | xargs rm)
 
 # NEWER CLEAN STEPS MUST BE AT THE END OF THE LIST
 # ************************************************