let
  pkgs = import <nixpkgs> { };
in
pkgs.runCommand "diagnostics-multiuser" { } ''
  set -x
  # no cache: ${toString builtins.currentTime}
  # For reproducibility, nix always uses nixbld group:
  # https://github.com/NixOS/nix/blob/1dd29d7aebae706f3e90a18bbfae727f2ed03c70/src/libstore/build.cc#L1896-L1908
  test "$(groups)" == "nixbld"
  touch $out
''