Here comes the cavalry. The embattled St. Mark’s Bookshop is gearing up for the arrival of the liberal icon Michael Moore, who just announced on Twitter that tonight all royalties from sales of his book, “Here Comes Trouble,” will go to the Occupy Wall Street protests. Mr. Moore is expected to arrive at 7 p.m. at the store on Third Avenue at Stuyvesant Street. The Local’s intrepid reporter, Liv Buli, will be on hand to get his opinion regarding the bookshop’s predicament. If you spot her, say hello!