The filmmaker who made Arnold Schwarzenegger a household name in the 1977 film “Pumping Iron” is making an IMAX documentary about NASA’s dual rover mission to Mars. George Butler previewed his project here Tuesday at Flight School 05 and PC Forum, a combined meeting of top space industry officials and entrepreneurs as well as leaders in the tech industry. Several people in the small audience expressed awe at both the mission’s scope and the telling of the story in the film, titled “Mars.”