{ builder ? ./combined-builder.sh }:

derivation {
  system = builtins.currentSystem;
  name = "nixos-size-combined";
  inherit builder;

  sp1 = builtins.storePath /run/current-system;
  sp2 = builtins.storePath /run/booted-system;

  preferLocalBuild = true;
  allowSubstitutes = false;
}