Cannes: Compelling newcomer Naomi Cosma plays an exchange student in a drama about the shock and trauma of 9/11 that cuts deep. In Katharina Rivilis’ sure knockout of a film “I’ll Be Gone in June,” two worlds of stifling teenage solitude collide at the same time as America mournfully recovers from the jihadist hijacking of four commercial airliners in September 11, 2001, which led to the leveling of the World Trade Center’s Twin Towers and the U.S. government’s colonial “war on terror” in