Refactor test filtering

Author: hamishmack

test/sublib-docs/default.nix

@@ -13,7 +13,7 @@ let
 
 in recurseIntoAttrs {
   # Haddock is not included with cross compilers currently
-  meta.disabled = pkgs.haskell-nix.haskellLib.isCrossHost;
+  meta.disabled = haskellLib.isCrossHost;
   ifdInputs = {
     inherit (project) plan-nix;
   };