ghc 7.8.3
ghc: bump bundled Cabal version to 1.18.1.4

Otherwise, attempting to `brew install cabal-install` will still fail,
despite forcing cabal-install's bootstrap script to use Cabal 1.20.0.2
instead of Cabal 1.20.0.0.
ghc: update 7.8.3 bottle.

Closes #31664.