This is bad advice. You can't diagnose poor patellar tracking from painless crepitus. He has NO pain.. . therefore this advice is terrible. Sure, strengthen your glutes and VMO anyway, everyone needs a stronger ass, but don't focus on it.
In a perfect world, we would all have smooth articular cartilage that would rub perfectly over the cartilage on the opposite side of the joint. But this is real life, and everyone has some amount of rough, or worn down cartilage. When 1 rough surface rubs on another, you get that grinding, cracking sound - crepitus. I have the loudest knees out of anyone I know, and I have now for about 5 years... No issues.
Don't worry about the cracking my friend, but like the other guy said, when it becomes painful, then you take care of it.