First of all, I don't know a lot about lions, but I don't see how a lion could swallow a whole brick. A piece of one, maybe. And if it was a big enough piece, left untreated, he would die. Probably within a few hours. It would mostly depend on what happened. It could perforate the esophagus, stomach, intestines. It could cause a blockage and cut off blood circulation to other organs.
Now if small enough, it could pass, but a large piece, not likely. The longer it stayed in the system without causing a problem, the longer he would live. It is possible to even die within a few minutes if it was large enough to get stuck in the esophagus, or actually got inhaled in the airway, and he would choke to death pretty quickly.
Side note, my dog used to eat pieces of bricks as a puppy. Chew them up small enough that they didn't cause any problems. But I have worked in emergency veterinary medicine, and seen many problems with foreign body obstructions. Even during surgery they can die if the damage is extensive enough.