Mitigate https://gitlab.haskell.org/ghc/ghc/-/issues/21250

GHC issue [#21250](https://gitlab.haskell.org/ghc/ghc/-/issues/21250) involves GHC 8.0.1 or 8.0.2 panicking, seemingly due to the presence 'corrupt' `*.hi` or `*.o` files from previous builds.

When those files are in `.stack-work`, that can resolved by `stack purge`. However, that is not a solution when they are in the `setup-exe-src` directory of the Stack root.
