Filming in a newly built prison camp near Trebujena, Spain, Steven Spielberg is providing impoverished townspeople with jobs, money and a little limelight. Spielberg chose the Andalusian setting for "Empire of the Sun," his new $30-million movie about a British boy interned in a World War II Japanese prison camp in Shanghai. Besides the prison camp, Spielberg built a landing strip for World War II aircraft, a huge sports stadium and a model of wartime Shanghai. Manuel Ruiz, local leader of the Communist-led Worker Commissions union, said the union had initially balked at Spielberg's policy of hiring extras on the spot instead of going through the local employment office. "The truth is, we couldn't provide the 50 people a day he needed to hire," Ruiz said. "We got the fee raised to $40 a day plus meals from the $32 they first offered. It is a satisfactory deal."