SoftBank’s chip designer Arm Holdings is set to debut on the Nasdaq on Thursday, in what is expected to be the biggest test for the U.S. IPO market after a listing drought that lasted for nearly 16 months. The company on Wednesday priced its offering of 95.5 million American Depositary shares at $51 apiece, fetching $4.87 billion for SoftBank at a valuation of $54.5 billion, with participation from cornerstone investors including Apple, Intel and Alphabet. How SoftBank played it safe in pricing Arm’s IPO Arm will be back as a publicly traded firm after seven years. Its shares used to…