plumb support for building for Android through Bazel

Sets up the ability to pull in packages published to Maven for Android development.
Adds a platform for targeting Android devices, invoked with:
--platforms=//bazel/platform:android_arm

Also fixes an icu BUILD path

Change-Id: I2e6079a4286c4c09af00866eb89d68c961c080cd
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/643302
Reviewed-by: Kevin Lubick <kjlubick@google.com>
Commit-Queue: Jorge Betancourt <jmbetancourt@google.com>
4 files changed