fixes for when (subpackage) pkg-ver already installed
    
    macros.ghc no longer uses ghc-pkg-wrapper
    
    - %ghc_fix_rpath gets lib dir directly by globbing buildroot
    - %ghc_gen_filelists reads pkg key from .conf
    - ghc-deps.sh: read unique pkg id from .conf
    
    before this preinstalled libs were interfering and this was further
    exasperated on ghc8 where .conf filenames are not keyed so we were querying
    `ghc-pkg list pkg` instead of pkg-ver.