SAN FRANCISCO :Apple CEO Tim Cook signaled on Thursday the iPhone maker was ready to spend more to catch up to rivals in artificial intelligence by building more data centers or buying a larger player in the segment, a departure from a long practice of fiscal frugality. Apple has struggled to keep pace with rivals such as Microsoft and Alphabet's Google, both of which have attracted hundreds of millions of users to their AI-powered chatbots and assistants. That growth has come at a steep cost,