CHANGMINGZHEN, China — The smell, salty and pungent, wafts through the freshly paved streets near the gleaming new factory. The factory is owned by a company called Laoganma, which makes a piquant chili-and-soybean sauce famous across China for its power to set mouths watering. In a time of global pandemic, when the jobs of working people around the world hang in the balance, the factory’s scents signal opportunity. Since it opened in March, when China was still in the grip of Covid-19, the factory has struggled to find enough machinery operators or quality control technicians. Now workers are flocking to Changmingzhen, a once-quiet farming town ringed with green mountains and rice paddies, from which young people once fled for better jobs elsewhere.