Avoid IFD (#1640)

I forgot this also avoids and IFD when I suggested it could be removed. See #1588

Author: hamishmack

modules/hackage-project.nix

@@ -26,6 +26,9 @@ in {
     # Avoid readDir and readFile IFD functions looking for these files in the hackage source
     # `mkOverride 1100` means this will be used in preference to the mkOption default,
     # but a `mkDefault` can still override this.
+    cabalProject = lib.mkOverride 1100 ''
+      packages: .
+    '';
     cabalProjectLocal = lib.mkOverride 1100 null;
     cabalProjectFreeze = lib.mkOverride 1100 null;
     src =