Add --exclude-sources to AAPT2 link

Information about where resources are defined can make having
reproducible builds more difficult, makes the generates resources.pb
large, and can exposes details about the machines that compiled the
resources.

The --exclude-sources flags can only be used when building a proto APK
and prevents source information from being included in the generated
resources protobuf.

Bug: 134929532
Test: checked debug string with and without the string
Change-Id: Ia345f067fe781ea82a4bcad37eb55576c72c44d7