NEW YORK—The family of late South African President Nelson Mandela is selling the anti-apartheid leader’s personal belongings to help pay for a memorial garden being built in his honor. Among the roughly 100 items are the colorful patterned Madiba shirts he wore on formal occasions, including to meet Britain’s Queen Elizabeth in 1998 and 2003. These shirts “brought joy to the great leader” and set him apart from other politicians, said Arlan Ettinger, president of New York-based auction house Guernsey’s, which will host a live and online auction on Dec. 11. Gifts from former U.S. President Barack Obama and other heads of state, as well as Mandela’s glasses, briefcases, and pants, are also on sale to fund the Nelson Mandela Freedom Garden in Qunu, South Africa where he is buried. He died in 2013 at age 95 at home in Johannesburg. Items that showcase Mandela’s family life will be saved …