I do what any normal driver would do. I turn off my cruise and coast down a few mph. He gets closer, so I tap my brake lightly just to turn on the lights, not affecting speed, but warning the guy that he's playing a very very bad game.
ummm, no normal driver would purposely brake when someone is coming fast up behind you. thats stupid, you could be at fault for potentially causing an accident. a normal driver would have just passed the truck and moved on and let the car go by.