American Giant’s Bayard Winthrop on how the pandemic has upended the apparel manufacturer, from cutting costs to converting factories — Coronavirus Diaries From the C-Suite is a new Marker series where leaders share how the pandemic is impacting their businesses. Eight years ago, when Bayard Winthrop founded American Giant, a San Francisco-based manufacturer of T-shirts, hoodies, and other apparel, he never imagined he would be running the business out of…