ScAS : Upgrade mill

[rjolly]

No description provided.

[hamzaremmal]

Thanks @rjolly for the quick reaction to rjolly/scas#4

[odersky]

It seems we still have a problem. scas is making all builds failing.

[WojciechMazur]

It's strange, the errors suggest it might be using some version of mill build using Scala 2, even though the build and boostrap script both use mill 1.0.5 as default. I think it might be caused by mill server running in the background - some of other projects that started previously could have started the mill server, and it's being reused, even though its not compatible. I think I have observed issues like that in the OpenCB. Let me check if I can provide a hotfix

[WojciechMazur]

We've been setting MILL_VERSION env variable which has higher priority then other ways of setting version, although it was deprecated and no always respected. I probably was forcing usage of mill 0.10.15 for mill 1.0.5 project
#24208