WASHINGTON — The U.S. Justice Department has sent a letter to Elon Musk’s super PAC warning that the billionaire Tesla CEO’s $1 million giveaways may violate federal law, several media organizations reported on Wednesday, citing people briefed on the matter. A letter from the department’s public integrity section, which investigates potential election-related law violations, went to the PAC. The Justice Department and Musk’s America PAC did not immediately respond to a request for comment. South African-born Musk, who has thrown his support behind Republican presidential candidate Donald Trump ahead of the November 5 election, announced on Saturday while speaking before