Cabal 1.22 -> Prelude.read -> no parse

As said in https://github.com/JPMoresmau/eclipsefp/issues/260, BuildWrapper fails with Prelude.read: no parse when using Cabal 1.22.
The setup-config file has changed to be in binary, and the code used via dynamic-cabal did a simple read that doesn't work any more. We need to use the Cabal API proper to read that file.
