CHANDLER, Ariz. (Reuters) - From a wind-swept industrial site in the Sonoran Desert, Intel Corp. (INTC.O: Quote, Profile, Research) , appears to be gearing up for battle. Construction crews hammer away at an unprecedented $2 billion upgrade to one of Intel's two Arizona factories, preparing the world's largest chip maker to safeguard its lead in manufacturing from resurgent rivals and to put recent costly missteps behind it. The stakes are high: If Intel can pull off its complex renovation of the 8-year-old Fab 12 plant, it could pioneer a much cheaper alternative to building chip fabrication facilities from scratch. For...