nixos/top-level: Remove unused builder variables

These variables were previously used by the activation script
build commands, but are now embedded into those commands for
to improve reusability for an upcoming addition.

nixos/modules/system/activation/top-level.nix

@@ -81,13 +81,7 @@ let
     passAsFile = [ "extraDependencies" ];
     buildCommand = systemBuilder;
 
-    # Some of these variables may be unused, but without certainly, removing
-    # them runs a risk of breaking out of tree systemBuilderCommands
-    inherit (pkgs) coreutils;
     systemd = config.systemd.package;
-    shell = "${pkgs.bash}/bin/sh";
-    su = "${pkgs.shadow.su}/bin/su";
-    utillinux = pkgs.util-linux;
 
     kernelParams = config.boot.kernelParams;
     nixosLabel = config.system.nixos.label;