message: tell users how to disable the leak check
diff: @@ -302,7 +302,10 @@ pub fn eval_main<'tcx>(tcx: TyCtxt<'tcx>, main_id: DefId, config: MiriConfig) ->
  if !ignore_leaks {
  // Check for thread leaks.
  if !ecx.have_all_terminated() {
  - tcx.sess.err("the main thread terminated without waiting for all remaining threads");
  + tcx.sess.err(
  + "the main thread terminated without waiting for all remaining threads",
  + );
  + tcx.sess.note_without_error("pass `-Zmiri-ignore-leaks` to disable this check");
  return None;
  }
  // Check for memory leaks.
  @@ -310,6 +313,7 @@ pub fn eval_main<'tcx>(tcx: TyCtxt<'tcx>, main_id: DefId, config: MiriConfig) ->
  let leaks = ecx.memory.leak_report(&ecx.machine.static_roots);
  if leaks != 0 {
  tcx.sess.err("the evaluated program leaked memory");
  + tcx.sess.note_without_error("pass `-Zmiri-ignore-leaks` to disable this check");
  // Ignore the provided return code - let the reported error
  // determine the return code.
  return None;
  