Open this photo in gallery: An Alibaba sign on a building in the Xuhui district in Shanghai, China, on Feb. 21.HECTOR RETAMAL/AFP/Getty Images Alibaba Group BABA-N Chairman Joe Tsai said on Tuesday the tech giant would recommence hiring, emboldened with more confidence following President Xi Jinping’s February meeting with business entrepreneurs. He also expressed concern about some very big investment announcements in artificial intelligence in the U.S., saying it could be the start of a bubble. Tsai lauded the rare meeting between Xi and big names in Chinese tech, including Alibaba co-founder Jack Ma, which marked a distinct thawing in…