Based on the android example that's in the cpal repo, this test plays
a 440hz sine wave and is based on GameActivity
Note: this requires a workaround branch for cpal that comments out
a dev-dependency on ndk-glue that cpal has for its android example.
This is needed because Cargo is spuriously propagating this dev
dependency outside of the cpal package (which leads to a crash)
Robert Bragg