Ryan Scott authored May 10, 2023 and Zubin committed Sep 19, 2023

This partially reverts some of the changes in !9475 to make `base` and
`ghc-prim` depend on the `mingwex` library on Windows. It also restores the
RTS's stubs for `mingwex`-specific symbols such as `_lock_file`.

This is done because the C runtime provides `libmingwex` nowadays, and
moreoever, not linking against `mingwex` requires downstream users to link
against it explicitly in difficult-to-predict circumstances. Better to always
link against `mingwex` and prevent users from having to do the guesswork
themselves.

See ghc/ghc!10360 (comment 495873) for
the discussion that led to this.

(cherry picked from commit 2b1a4abe)