Staging directory does not update when changing build device type

This is a bit of an obscure case maybe, but QTCREATORBUG-32433 lead to the wrong build device type for boot2qt kits on macOS.

After opening a project, the value for the "Staging directory" is set to a temporary path on macOS (some /var/folders/....).

After switching the kit to the correct build device (Docker Device) that (default) staging directory doesn't change to the new default (some /tmp/....), and the set value is not accessible on the Docker device, leading to confusing errors about CMake not being able to access the directory. And since the user never touched, and probably doesn't even knows about the staging directory, it is pretty unclear where that error comes from and how to fix it.

That said, closing and reopening the project (or QtC) sets the correct new default staging directory, so "have you tried turning it off and on again" is a workaround.