Gilead stock is flashing "buy" in bright green letters.Biopharmaceuticals stock Gilead Sciences (GILD 2.70%) jumped 2.5% through 12:30 p.m. ET Friday after Needham & Co. upgraded the shares to a buy rating and slapped a $133 price target on the $116 stock.Key to the analyst's analysis is Gilead's new Yeztugo prescription medication for pre-exposure prevention of HIV-1. What Needham says about GileadCiting a survey of physicians, Needham reports in a note covered on The Fly this morning that the market for ...