IBM Corp was sued on Monday by a shareholder that said it committed securities fraud by failing to write down a money-losing semiconductor unit before agreeing to pay another company $1.5 billion to take that unit off its hands. The lawsuit filed in Manhattan federal court arose from IBM’s announcement last Oct. 20 that it would sell the unit to GlobalFoundries Inc, and take a related $4.7 billion pre-tax charge. Warren Buffett’s Berkshire Hathaway Inc is among IBM’s largest shareholders.