Changing dune lang version triggers compiler rebuild

[Alizter]

For whatever reason, bumping dune-project's dune lang version triggers a compiler rebuild. I went from 2.0 to 3.16 and the compiler is being rebuilt from scratch.

[shonfeder]

I guess this is related to #12103, at least in the abstract? Do we suppose that they species of the same general problem?

[sabine]

I'm going to look into this as my first issue onboarding onto Dune.

[shonfeder]

We agreed that this was not critical for the MSP in our team meeting.