NEW YORK—Rivian Automotive, a company that has delivered about 150 electric pickup trucks mostly to employees, has surpassed General Motors to become the nation’s second most valuable automaker. The California company’s market valuation exceeded Ford’s in its first day a public company Wednesday. Its shares rose 10 percent at the opening bell Thursday pushing its valuation over $90 billion. That’s greater than Detroit’s GM, one of the biggest auto manufacturers in the world, which sold more than 2.5 million vehicles last year. Rivian’s goal this year is to produce 1,000 electric vehicles. The company rolled out its first vehicle, the R1T electric truck, in September and plans to launch its electric SUV, the R1S, in December. Ford is one of Rivian’s high-profile backers, having invested a half-billion dollars into the company in 2019. The other is Amazon, which held a 20 percent stake in Rivian ahead of the initial public …