SoftBank Group Corp. is building up stakes in Nvidia Corp. and Taiwan Semiconductor Manufacturing Co., the latest reflection of Masayoshi Son’s focus on the tools and hardware underpinning artificial intelligence. The Japanese technology investor raisedBloomberg Terminal its stake in Nvidia to about $3 billion by the end of March, up from $1 billion in the prior quarter, according to regulatory filings. It bought around $330 million worth of TSMC shares and $170 million in Oracle Corp., they sho...