It would be useful to have support for building against the Android NDK in the repository as well as the depends system.

Greenaddress is currently doing this and has scripts and patches for doing so in a separate repository.

Integrating this into the upstream build would likely be more maintainable, and it would make it possible to make the ndk build part of the gitian build set at some point, providing higher reassurance for the Android executables.

(sister issue for iOS is #11720)