nixos/glasgow: add glasgow to systemPackages

That's what various other tools in hardware.* do, it's surpising if
`hardware.glasgow.enable` does not actually give you the `glasgow`
binary in `$PATH`.

nixos/modules/hardware/glasgow.nix

@@ -22,6 +22,7 @@ in
   };
 
   config = lib.mkIf cfg.enable {
+    environment.systemPackages = [ pkgs.glasgow ];
     services.udev.packages = [ pkgs.glasgow ];
     users.groups.plugdev = { };
   };