Hello,

The 'remove-unnecessary-references' phase in GHC added by commit
f737d3ddd8018f89b0fa9f80aee4490cd726903a introduces a regression where
users with a non-standard store prefix will get a different end result.

The code should be changed to use %store-directory instead of
hard-coding "/gnu/store".

While at it, it would be good to add '#:disallowed-references ("doc")'
to catch regressions in that area.