Federal authorities announced the arrests yesterday of four construction supervisors and 76 illegal immigrants at a Kentucky home-building company, continuing a promised government crackdown on employers that rely on illegal labor. The arrests at Fischer Homes, a leading builder in Kentucky, Indiana and Ohio, followed the April 19 arrests of seven current and former managers and more than 1,100 workers for Ifco Systems North America Inc., a subsidiary of a Dutch manufacturer of plastic crates and wooden pallets. The effort comes as Congress debates plans to overhaul the nation's immigration laws. "We will continue to bring criminal actions against employers...