Syntax check generated Android.bp snapshot

Checks the syntax of the Android.bp file generated for the sdk
snapshot. While this will not detect all possible problems with the
generated Android.bp file it will detect some and it is far better to
detect those issues during generation than when it is unpacked and
used.

Bug: 155628860
Test: m nothing
Change-Id: Ieec86a7a49fa2e3bd8b9f83aca540114232a3476