haskell: disable haddock on GHC <7.8 on darwin

Fixes NixOS/nixpkgs#812

Changed files
+1 -1
pkgs
development
haskell-modules
+1 -1
pkgs/development/haskell-modules/generic-builder.nix
···
, jailbreak ? false
, license
, maintainers ? []
-
, doHaddock ? true
+
, doHaddock ? !stdenv.isDarwin || stdenv.lib.versionAtLeast ghc.version "7.8"
, passthru ? {}
, pkgconfigDepends ? [], libraryPkgconfigDepends ? [], executablePkgconfigDepends ? [], testPkgconfigDepends ? []
, platforms ? ghc.meta.platforms