“Harry Potter” has landed — at Warner Bros. Industry sources say that the movie script based on J.K. Rowling’s runaway bestseller “Harry Potter and the Sorcerer’s Stone” has been delivered by screenwriter Steve Kloves, who wrote “The Fabulous Baker Boys,” and that Kloves has remained faithful to the bestseller. The plot deals with Harry, a 10-year-old wizard, and his matriculation at Hogwarts School of Witchcraft and Wizardry. Though the cost of the film could run as high as $100 million, with $45 million of that expected to be spent on special effects alone, the sheer popularity of the three existing Potter books (there are four more to come) — which have sold 17 million copies — is stemming any worry about cash flow on the project. An unknown British child actor is expected to nab the coveted role of Harry. As for directing the picture, Steven Spielberg is Warners’ leading contender, though other names mentioned have been Barry Levinson (“Rain Man” and the current “Liberty Heights”), Chris Columbus (“Home Alone” and the upcoming “Bicentennial Man”) and Rob Reiner (“When Harry Met Sally…”).