Not sure what you're suggesting here...
I think I covered that in my last line
More investigation and design to be done to make sure I'm not over thinking things.
Multi-target is going to make things more complex and I'm not sure the command line args are the right approach. But I'm not sure yet.
That said, we are running into issues where applying -Xcc to all targets is causing problems in cross scenarios. So we may need to do something in the short term. That's covered here: Swift on STM32C011