BYD Co., the Chinese electric-car maker backed by Warren Buffett, said it is now the world’s biggest face-mask maker after starting production less than a month ago to fight the coronavirus outbreak. The company can make 5 million masks a day and is further expanding capacity, it said Friday in a statement. Founder Wang Chuanfu led a team of 3,000 engineers to build production lines from scratch using 90% in-house components. BYD didn’t specify what type of masks it makes. BYD also said to produce around 300,000 bottles of hand sanitizers a day.