Move super.img to obj/PACKAGING

To avoid the confusion. super.img isn't intended to be flashed
during day-to-day development.

Test: m superimage
Bug: 128891161
Change-Id: I9d62e5929b415343b2d890ab21e6ae51175af2ae
diff --git a/CleanSpec.mk b/CleanSpec.mk
index 3d9a1ef..76bc0c5 100644
--- a/CleanSpec.mk
+++ b/CleanSpec.mk
@@ -613,6 +613,8 @@
 
 # Clean up old location of system_other.avbpubkey
 $(call add-clean-step, rm -rf $(PRODUCT_OUT)/system/etc/security/avb/)
+
+$(call add-clean-step, rm -rf $(PRODUCT_OUT)/super.img)
 # ************************************************
 # NEWER CLEAN STEPS MUST BE AT THE END OF THE LIST
 # ************************************************