apkcerts: Add information about the compressed state of the APK.

We add a compressed="$extension" attribute to an APK's entry if it's
compressed.

Bug: 64531948
Test: make dist

Change-Id: Ic3f95ed77f0bb16dec825bae944c70ee2d130657
diff --git a/core/package_internal.mk b/core/package_internal.mk
index 28c3a08..2eb806c 100644
--- a/core/package_internal.mk
+++ b/core/package_internal.mk
@@ -222,6 +222,7 @@
 endif
 
 ifdef LOCAL_COMPRESSED_MODULE
+PACKAGES.$(LOCAL_PACKAGE_NAME).COMPRESSED := gz
 LOCAL_BUILT_MODULE_STEM := package.apk.gz
 LOCAL_INSTALLED_MODULE_STEM := $(LOCAL_MODULE).apk.gz
 else  # !LOCAL_COMPRESSED_MODULE