Forcing alsa on android with some feature

[ofluffydev]

I'm sure this seems like a very niche thing, but right now the default features and conditional compilation use some android backend if built on android. But, this also happens when you compile a project in tmux on an android phone, making the audio not work. Tmux seems to be capable of running and handling ALSA somewhere, and I think it would be cool to be able to build something specifically for that on android.

[roderickvd]

Sure, I'd be open to that if someone would put in a PR for it. I don't have hardware to test that on myself.