Summary:
This diff is cleaning up some configurations in the `Android.mk` files
of the native build. Specifically I simplified some of the rules and removed
a duplicate file specification.
Changelog:
Internal - Cleanup warnings in the NDK build
Reviewed By: ShikaSD
Differential Revision: D30220715
fbshipit-source-id: a100953fe977879a6d28cb0a2ef4b3358fb7c774