Add support for configuring legacyPackages

builtinModules/legacyPackages.nix

@@ -0,0 +1,19 @@
+# flakelight -- Framework for simplifying flake setup
+# Copyright (C) 2023 Archit Gupta <archit@accelbread.com>
+# SPDX-License-Identifier: MIT
+
+{ config, lib, genSystems, ... }:
+let
+  inherit (lib) mkIf mkOption;
+  inherit (lib.types) functionTo nullOr pkgs;
+in
+{
+  options.legacyPackages = mkOption {
+    type = nullOr (functionTo pkgs);
+    default = null;
+  };
+
+  config.outputs = mkIf (config.legacyPackages != null) {
+    legacyPackages = genSystems config.legacyPackages;
+  };
+}