Unity: Expose an isQuitting variable to use when spawning things in OnDestroy

GameStateUtility.cs

public static class GameStateUtility {
    public static bool isQuitting { get; private set; }

	[RuntimeInitializeOnLoadMethod( RuntimeInitializeLoadType.SubsystemRegistration )]
    static void Init () {
        isQuitting = false;

        Application.quitting += () => {
            isQuitting = true;
        };
    }
}

Sample.cs

public class MyBehaviour : MonoBehaviour {
  void OnDestroy () {
    if( !GameStateUtility.isQuitting ) {
      // spawn your objects.
    }
  }
}