cabal repl and the Paths_mypackage module

I'm not sure if this is intended behavior, but I'd expect the `Paths_` module to point somewhere meaningful when I'm running in `cabal repl`. It seems to point to my user directory when I'd expect it to point to the current package root.

Start by reproducing the behavior with `cabal repl` and inspect how the `Paths_` module is generated or resolved during that command. The work is done when the module points to the current package root rather than the user's directory, with the behavior verified in a relevant test if one exists.

Written by the indexing model from the issue text.