Pastel proved that the LLVM path works well for all the architectures we
care about for Android. Converted all aspects of the build to Android.bp

Bug: b/139147241
Change-Id: I8ad8c2cc816fbb313feaf4a0c4d3dcf40cff37af
Reviewed-on: https://swiftshader-review.googlesource.com/c/SwiftShader/+/35168
Kokoro-Presubmit: kokoro <noreply+kokoro@google.com>
Reviewed-by: Ben Clayton <bclayton@google.com>
Reviewed-by: Nicolas Capens <nicolascapens@google.com>
Tested-by: Chris Forbes <chrisforbes@google.com>