Override Cabal's library visibility check on GHC <8.8

GHC <8.8 isn't able to read the "visibility" field from the package
database, since it's built against an older Cabal. For this reason,
using multiple public libraries with it did not work (all sublibraries
appeared as private).

This patch makes cabal-install override Cabal's library visibility
checks when GHC is older than 8.8, extending the multiple libraries
feature compatibiliy to older GHCs.