Disable haskell-gi-overloading (it's too slow to build)

Author: hamishmack

test/gi-gtk/default.nix

@@ -8,6 +8,8 @@ let
     inherit compiler-nix-name evalPackages;
     src = testSrc "gi-gtk";
     cabalProjectLocal = builtins.readFile ../cabal.project.local + ''
+      -- The overloading feature of haskell-gi makes build times very long
+      constraints: haskell-gi-overloading ==0.0
       if impl(ghc >=9.11)
         constraints: filepath source
     '';