Android ARM-64 Build

[jerinphilip]

Adds a CI using Android NDK and changes to CMakeLists.txt to build on Android.

PRs to be merged before this:

• https://github.com/browsermt/marian-dev/pull/79
• https://github.com/browsermt/ssplit-cpp/pull/13

Issues:

• ARM only supports int8, int8Alpha, int8AlphaAll. The *shift* versions are unusable. Supplied configuration files from models in translateLocally.json comes with an x86_64 assumption which will need platform detect and choosing at each client.

[jerinphilip]

https://github.com/browsermt/marian-dev/commit/3a6c51516670eaca3e841ccb76840208091f3278

[2022-06-15 10:35:46] [data] Lexical short list firstNum 50 and bestNum 50
[2022-06-15 10:35:46] gemm-precision: *shifted* is not available on ARM; Setting to false.
[2022-06-15 10:35:46] [memory] Extending reserved space to 2048 MB (device cpu0)
[2022-06-15 10:35:46] Loaded model config
[2022-06-15 10:35:46] Loading scorer of type transformer as feature F0
[2022-06-15 10:35:47] [memory] Reserving 31 MB, device cpu0
[2022-06-15 10:35:47] [memory] Reserving 8 MB, device cpu0
[2022-06-15 10:35:47] Best translation 0 : Hallo Welt!
Hallo Welt!
[2022-06-15 10:35:47] Total time: 0.02579s wall