Require mesa package for steam rather than gamescope

system/gamescope.nix

@@ -1,6 +1,5 @@
-{ pkgs, user, ... }: {
+{ user, ... }: {
   imports = [ ./default.nix ./steam.nix ];
-  environment.systemPackages = with pkgs; [ mesa ];
   sound.enable = true;
   hardware = {
     pulseaudio.enable = false;

system/steam.nix

@@ -1,4 +1,5 @@
-{ ... }: {
+{ pkgs, ... }: {
+  environment.systemPackages = with pkgs; [ mesa ];
   hardware = {
     opengl.driSupport32Bit = true;
     steam-hardware.enable = true;