Fix nix CI

Author: alexfmpe

default.nix

@@ -9,10 +9,11 @@
     (drv: {
       testSystemDepends = (drv.testSystemDepends or []) ++ [ (if postgresql == null then pkgs.postgresql else postgresql) ];
     });
-  gargoyle-postgresql-nix = pkgs.haskell.lib.overrideCabal
-    (haskellPackages.callCabal2nix "gargoyle-postgresql-nix" ./gargoyle-postgresql-nix {})
-    (drv: {
-      librarySystemDepends = (drv.librarySystemDepends or []) ++ [ (if postgresql == null then pkgs.postgresql else postgresql) ];
-    });
+
+  gargoyle-postgresql-nix = haskellPackages.callCabal2nix "gargoyle-postgresql-nix" ./gargoyle-postgresql-nix {
+    # TODO: libpq will become standalone in https://github.com/NixOS/nixpkgs/pull/359659
+    libpq = postgresql;
+  };
+
   gargoyle-postgresql-connect = haskellPackages.callCabal2nix "gargoyle-postgresql-connect" ./gargoyle-postgresql-connect {};
 }