message: work harder around notorious macos unrealiability
diff: @@ -81,7 +81,9 @@ fn check_conditional_variables_timed_wait_notimeout() {
  cvar.notify_one();
  });
  - let (_guard, timeout) = cvar.wait_timeout(guard, Duration::from_millis(1000)).unwrap();
  + // macOS runners are very unreliable.
  + let timeout = if cfg!(target_os = "macos") { 2000 } else { 500 };
  + let (_guard, timeout) = cvar.wait_timeout(guard, Duration::from_millis(timeout)).unwrap();
  assert!(!timeout.timed_out());
  handle.join().unwrap();
  }
  