When the "sdk_repo" modified is used during the SDK build,
this also generates the repository.xml and addon.xml files
for the new SDK repository packages and places them in
the DIST_DIR.
Example usage:
make -j 16 PRODUCT-sdk-sdk showcommands sdk_repo dist DIST_DIR=/dist/sdk
make -j 16 PRODUCT-google_sdk-sdk_addon showcommands sdk_repo dist DIST_DIR=/dist/addon
Change-Id: Ibaad66f4b1cc476a4146afde7087a10a0557f74c