My friend built a house and just sold it 10 months ago. He had all the right permits, and had every stage inspected and signed off by the local building inspector. When he sold, the buyer had a inspection done and there were no problems. 10 months later the buyer tells my friend he's ripped the basement apart and has problems with the house, and is suing him. Can he do this?

It would depend on the problem. He can sue for anything he wants but the question is if he would win or not
But most likely he wouldn't unless he can prove it was pre existing and the seller intentionally hid it then maybe. But it sounds like it was something the buyer messed up and is trying to take it out on the seller.