RIYADH, Saudi Arabia — President Trump got the royal treatment on his first stop in Saudi Arabia, as white Arabian horses flanked his motorcade — with adviser Elon Musk in tow. Dozens of Saudis rode on horseback carrying US and Saudi flags as Trump’s motorcade peeled into the Royal Court, where he got a warm welcome before going to a lunch in the palace adorned with chandeliers and marble floors. “I really believe we like each other a lot,” Trump told reporters after his arrival, referring to Saudi Arabia’s Crown Prince Mohammed bin Salman as a friend. He later recalled...