Using in vendored mode with additional internal extensions

[yoramdelangen]

I want to start using the project in vendored mode and add our own custom PHP extension. This means we should add additional 'sources' and 'ext' items to have a streamlined process with the project.

Is this already possible to achief? If so could you guide me a little or point me in a direction?

After digging around I think we need to add additional configuration into the BuilderPovider instance. I coulnd't find a proper way yet to add the addional configuration yet.