Currently custom devices only support debug mode. In the future, we could look at enabling release & profile mode.

This depends on #75823 (linux ARMv7 support).

Running the app is easily implemented:

• add runRelease and runProfile command in custom devices config (behaviour similiar to runDebug command)
• document those in the JSON schema

For building, we need ARMv7 artifacts (gen_snapshot, ideally also flutter engines). I'm not sure what layout other embedders expect, but for flutter-pi the finished app.so should be contained in the asset bundle.