What should I tell a guy friend that likes a girl when I know for sure the girl doesnt like him?

One of my friends recently told me who he likes knowing that I am friends with her. He has a low self confidence and keeps telling me how hes not going to do anything about this assuming no girl would ever say yes to him. I know my friend doesn’t like him and would nicely shut him down. So what should I tell him to do? I would like to give him courage, but I don’t wanna give him false hope when I know the outcome?