DUBLIN—Ireland dropped its opposition to an overhaul of global corporate tax rules on Thursday, agreeing to give up its prized 12.5 percent tax for large multinationals in a major boost to efforts to impose a minimum rate worldwide. Ireland, the low-tax European headquarters for blue chip companies including Apple, Google, and Facebook, declined to sign up to the initial deal in July, objecting to a proposed rate of “at least” 15 percent. An updated text this week dropped the “at least”, clearing the way for ministers to do what successive governments said they would never contemplate—giving up the low rate that has helped win Ireland investments and jobs for decades. “Joining this agreement is an important decision for the next stage of Ireland’s industrial policy—a decision that will ensure that Ireland is part of the solution,” Finance Minister Paschal Donohoe told a news conference. “This is a difficult and complex …