By Caroline Pailliez OTTMARSHEIM, France (Reuters) – When its employees started leaving in droves for better-paying jobs across the border in Switzerland, family-run French window maker Fligitter knew it needed to do something to retain staff. With surging raw material costs leaving little room to hike wages, Fligitter’s management seized on changes made in 2017 by President Emmanuel Macron to France’s strict labour laws that enable companies to offer tax-free bonuses in exchange for cutting both overtime pay and length of service salary rises. Last September the firm reached agreement with it…