Author the user story for this feature
As an app developer, I want to run robo tests without a robo script so I can sanity check my app before closing a pull request.

Is your feature request related to a problem? Please describe.
I already run instrumentation tests but need a full integration test of the release build.

I need to verify that release builds of my app won't crash immediately on launch since release builds are different.

Google Play prelaunch reports have caught a variety of obfuscator triggered issues, and they don't require a robo script. A robo script is not necessary for this (and is difficult for me to implement since my resource names are also obfuscated as part of my build process.)

Describe the solution you'd like
Allow Flank to run with just an APK. Currently Flank says "One of following options must be specified [test, robo-directives, robo-script]."

Describe alternatives you've considered
I can do this with gcloud directly, so this is a Flank limitation.

I tried supplying fake robo-directives to Flank, but it still gave me the error message "One of following options must be specified [test, robo-directives, robo-script]."