Continents collided on the Arabian Gulf on Thursday as China sold sovereign bonds denominated in U.S. dollars for the first time in three years — in Saudi Arabia. At $2 billion, the bond sale is too small to provide a serious boost to China’s foreign exchange coffers. But it does act as icing on the cake of investments that Saudi Arabia has poured into China over the past 12 months, many of which are distinct from the oil purchases that have long underpinned the two countries’ relations