Is your feature request related to a problem? Please describe:
When running from the editor, where DM_SERVICE_PORT is set to "dynamic", the engine uses a random port, but the system firewall blocks that port. This is a problem for content-less build, where the editor needs to communicate with the engine.

Describe the solution you'd like:
Add a check for the DM_SERVICE_PORT environment variable:

1. If DM_SERVICE_PORT exists and contains a specific port number, use that port
2. If DM_SERVICE_PORT is not set, fall back to current behavior of using a random port

Describe alternatives you've considered:
Using a bob.jar with DM_SERVICE_PORT environment variable set to a specific port number

Additional context (OPTIONAL):
https://forum.defold.com/t/solved-problem-with-contentless-android-app-build/75743/4