It'd be very advantageous to support x86 in run_cts.py, which would open up emulator support.

Debugging CTS failures can often be API-level dependent, which makes emulator very convenient (it's easier to provision an emulator than to flash a physical device).

Once we support multiple architectures, you can guess the device architecture with DeviceUtils.product_cpu_abi [1].

I wrote up docs for the cpu_abis we support [2]. The focus of the docs is "cpu.abi -> target_cpu," but you can probably figure out how to translate that to "--arch" values.

[1] https://cs.chromium.org/chromium/src/third_party/catapult/devil/devil/android/device_utils.py?l=2309&rcl=a9729f33472aa371f0e16e70dbada1d96ee20427
[2] https://chromium.googlesource.com/chromium/src/+/HEAD/docs/android_build_instructions.md#Figuring-out-target_cpu