A street kid fights for survival in Lebanon, in Nadine Labaki’s heart wrenching new film. Nadine Labaki is a Lebanese writer-director whose three feature films to date display a strong sensitivity to the lives of ordinary working people in Lebanon, their struggles, resilience, and humor. An actress herself, she is especially adept at bringing out the best in actors. Her latest picture, Capernaum, is a giant stride forward, proof that she is now a major filmmaker on the world stage. In Beirut, a 12-year-old boy named Zain is in prison for stabbing a man in the stomach. Zain is small…