Restrict vendor modules to help AOSP product distribution.

Bug: 5692177

If you set "PRODUCT_RESTRICT_VENDOR_FILES := true" in a product
configuration, this changes restricts that:
- No overlays in the vendor tree.
- No PRODUCT_COPY_FILES coming from the vendor tree.
- Any referenced package with Android.mk in the vendor tree must have
  LOCAL_MODULE_OWNER set to a value that's compared against a whitelist
  stored in the core build system.

Change-Id: I172b84c7c853e9a04bf9879ea8dec90bd5054230
diff --git a/core/clear_vars.mk b/core/clear_vars.mk
index 3a04b7b..6677941 100644
--- a/core/clear_vars.mk
+++ b/core/clear_vars.mk
@@ -115,6 +115,7 @@
 LOCAL_PROTOC_FLAGS:=
 LOCAL_NO_CRT:=
 LOCAL_PROPRIETARY_MODULE:=
+LOCAL_MODULE_OWNER:=
 
 # Trim MAKEFILE_LIST so that $(call my-dir) doesn't need to
 # iterate over thousands of entries every time.