I noticed that in revised haskell guidelines , there is mentioned
the ghc-rpm-macros package, which provides macros.ghc file, which in
turns provides some useful macros for packaging of Haskell packages.
I think originally the macros lived in the Fedora ghc package but
since ghc takes quite a long time to build and the binaries are
quite large, it made good sense to move them to their own package.
It also had made development simpler and cleaner, though of course
packages do need to BR ghc-rpm-macros, which I think is transparent.