(Feature Request) Support projects that do not use MXML in "royale serve"

The Royale CLI expects a "Main.mxml" in order to build then serve, it is optional on debug but a failure on release. On projects that use ActionScript only, and no MXML, it would be ideal to have another way to build.

Is it possible to add additional compile arguments, such as through metadata, in the MXML, or using `royale serve`? As a workaround, is there a way to write a simple MXML that does _not_ include the Royale runtime library, but only boots up a script?