refactor(nixGL): extract 'nixGL' wrapper

home/modules/lib.nix

@@ -0,0 +1,9 @@
+{ config, lib, ... }:
+
+{
+  options.nixgl.wrap = lib.mkOption {
+    type = lib.types.functionTo lib.types.package;
+    default = if config.lib ? nixGL then config.lib.nixGL.wrap else lib.id;
+    readOnly = true;
+  };
+}