Should base be linked implicitly?

[hsyl20]

base is now a normal package that can be reinstalled. Yet GHC will automatically link against a specific version of base for backward compatibility. This is done by storing base's unit-id in the settings. We don't do this for now in #3 because it means rewriting the settings after they have been used to compile boot libraries. It doesn't seem sane to mix inputs and outputs like this.

I agree with the comment on the upstream issue that we shouldn't do this.

Q: do we want to keep compatibility with upstream here?

In the meantime I'll mark T25382 as expect_broken as it fails on CI.