Publish multiple library versions with different NDK/STL

[ViliusSutkus89]

Current long term stable NDK dropped support for pre KitKat (api-19) devices. Multiple NDK versions would allow to support them longer.

Would be good to publish library linked against static STL. Multiple libraries can ship different shared STLs and produce file collissions. If those libraries are running on different processes, static STL would be easier to manage.