Automate additional priv-apps permissions

[osm0sis]

Something should be added to the crawler/build scripts to extract and automatically add new required permissions, I should think.

Originally posted by @osm0sis in #873 (comment)

The fix would go in add_sources.sh in the main repo. I do not have the time to add this but AOSP has a python script that is most of the way there.

Originally posted by @NicholasBuse in #873 (comment)

This would fix ongoing bad builds from updated APKs causing bootloops for the masses, which are only being fixed reactionarily currently.

AOSP script: https://android.googlesource.com/platform/development/+/master/tools/privapp_permissions/privapp_permissions.py

[WrekLess]

Hi @osm0sis,

I tried this myself today and added the output to privapp-permissions-platform.xml. There were only two Gapps that showed in the output.

`

<privapp-permissions package="com.google.android.backuptransport">
    <permission name="android.permission.MODIFY_NETWORK_ACCOUNTING"/>
</privapp-permissions>

<privapp-permissions package="com.google.android.pano.packageinstaller">
    <permission name="android.permission.CLEAR_APP_CACHE"/>
    <permission name="android.permission.DELETE_PACKAGES"/>
    <permission name="android.permission.MANAGE_USERS"/>
</privapp-permissions>

`

After applying, my build (tvstock/tvmini) completes but Leanback Launcher and Google stop working and ask to be restarted endlessly. I I can't get into settings to enable USB debugging to pull a logcat and see what's going on.