A firebug suspected of torching a landmarked 173-year-old Brooklyn church was busted Tuesday when an eagle-eyed cop spotted him shoplifting a turkey sandwich and donuts from a Midtown CVS, sources said. John Jones, 24, was hit with a federal arson rap after he was picked up trying to swipe a free meal with a Coke to wash it down in the store on Broadway at about 1:39 a.m., sources said.