swiftpm2nix: avoid top-level with in support module (#308838)

These functions are accessed from the following attrset paths:

- `swiftpm2nix.mkPinFile`
- `swiftpm2nix.helpers.sources`
- `swiftpm2nix.helpers.configure`

pkgs/development/tools/swiftpm2nix/support.nix

@@ -1,6 +1,6 @@
 { lib, fetchgit, formats }:
-with lib;
 let
+  inherit (lib) concatStrings listToAttrs makeOverridable mapAttrsToList nameValuePair;
   json = formats.json { };
 in rec {