A stranger stabbed a 28-year-old man in an unprovoked Thursday evening attack outside a John Jay College of Criminal Justice building, police said. The victim was knifed in the back around 7:10 p.m. in front of a building on 10th Avenue near West 59th Street, which houses the university’s historic Haaron Hall, home to the world’s largest criminal justice library, cops said.  He was taken across the street to Mount Sinai West hospital, where he is listed in stable condition, authorities said. It