The world’s biggest tech companies are facing disruptions to their supply chains from prolonged factory closures and labor shortages in China, as the deadly coronavirus outbreak threatens the nation’s vast manufacturing network. Electronics, telecom and semiconductor companies all rely on factories in China, honed to efficiency by years of servicing Western tech giants. Wuhan, the epicenter of the outbreak that is under lockdown by Chinese authorities, is home to numerous high-tech component suppliers and is a key…