backport some updates from rawhide 0.95.5:
- new cabal-tweak-dep-ver script to tweak depends version bounds in .cabal
- ghc-dep.sh: only use buildroot package.conf.d if it exists
- ghc-deps.sh: look in buildroot package.conf.d for program deps
- add a meta-package option to ghc_devel_package and use in ghc_devel_requires
- allow ghc_description, ghc_devel_description, ghc_devel_post_postun
to take args
- support meta packages like haskell-platform without base lib files
- add shell variable cabal_configure_extra_options to cabal_configure for
local configuration
- do not provide prof when without_prof set
