floooh
Android release apk signing not yet supported
See https://developer.android.com/tools/publishing/app-signing.html#signing-manually on how to sign manually. I did something that might work for fips, too already for CaveExpress (see https://github.com/mgerhardy/caveexpress/commit/9debf58437f76fce17da6f7a8e41953c4a1b7d47 ).
Maybe you have a better idea than environment variables... I would be glad to hear about it.
I don't have a better idea to offer how to handle the signing password at the moment. I'll try to improve the mobile stuff after I'm done with the Metal renderer. I'd like to add support for VisualStudio's recent Android/iOS support, and see what can be improved with Apple's recent change that one doesn't need to be a registered developer to run code on iOS devices.
cmake 3.4 has some interesting vstudio + android changes - see http://www.kitware.com/blog/home/post/1002