Convert libspirit to Android.bp

See build/soong/README.md for more information.

Test: cd frameworks/rs/rsov/compiler/spirit; mma
Test: out/host/linux-x86/nativetest64/word_stream_test/word_stream_test
Test: out/host/linux-x86/nativetest64/instructions_test/instructions_test
Test: out/host/linux-x86/nativetest64/pass_queue_test/pass_queue_test
Test: out/host/linux-x86/nativetest64/libspirit_test/libspirit_test
Change-Id: Ief9a282338f673877b381d2b68e115a83a80a96f