Test fixes

Author: hamishmack

test/gi-gtk/default.nix

@@ -8,7 +8,8 @@ let
     inherit compiler-nix-name evalPackages;
     src = testSrc "gi-gtk";
     cabalProjectLocal = builtins.readFile ../cabal.project.local + ''
-      constraints: filepath source
+      if impl(ghc >=9.11)
+        constraints: filepath source
     '';
   };