Use cabal.project.freeze if available

Currently callCabalProjectToNix does not copy `cabal.project.freeze`
from source directory, leading to different build plans when building
components with nix and when building project with `cabal new-build`
inside `nix-shell`.

This behavior is undesired, so this commits fixes it.

Author: maksbotan

lib/call-cabal-project-to-nix.nix

@@ -35,7 +35,7 @@ let
       inherit src;
       filter = path: type:
         type == "directory" ||
-        pkgs.lib.any (i: (pkgs.lib.hasSuffix i path)) [ ".project" ".cabal" "package.yaml" ]; }
+        pkgs.lib.any (i: (pkgs.lib.hasSuffix i path)) [ ".project" ".cabal" ".freeze" "package.yaml" ]; }
     else src;
 
   # Using origSrcSubDir bypasses any cleanSourceWith so that it will work when