Extract prebuilt APKs from zip files

Since APKs are zip files, embedded APKs in other APKs can be extracted,
installed, then optimized.

DPI-based filenames can be used if LOCAL_DPI_VARIANTS is set.

Bug: 29179775
Change-Id: Iab6388111522114ce9dc07057d59e3a89394cd6f
diff --git a/core/clear_vars.mk b/core/clear_vars.mk
index 59e907b..5886610 100644
--- a/core/clear_vars.mk
+++ b/core/clear_vars.mk
@@ -204,6 +204,8 @@
 # Used to replace the installed file of a presigned prebuilt apk in PDK fusion build,
 # to avoid installing the presigned apks with classes.dex unstripped.
 LOCAL_REPLACE_PREBUILT_APK_INSTALLED:=
+LOCAL_EXTRACT_APK:=
+LOCAL_EXTRACT_DPI_APK:=
 
 # arch specific variables
 LOCAL_SRC_FILES_$(TARGET_ARCH):=