Summary:
This adjusted the C++ output for Android codegen (NativeModule specs) so we can compile it with ndk-build in Gradle:
* Use `#include` instead of `#import` for header files
* Added `#pragma once`
* Removed direct include of `<fb/fbjni.h>` -- this is not necessary
* Added generated Android.mk file based on library name
Changelog: [Internal]
Reviewed By: shergin
Differential Revision: D23809082
fbshipit-source-id: 11ddfea7b48c8b2eb6efe885641ace4fc327d50d
Kevin Gozali
8cca54a7a7