[unwind] Handle UNW_X86_64_RIP register In some binaries, built with clang/lld, libunwind crashes with "unsupported x86_64 register" for regNum == 16: Differential Revision: https://reviews.llvm.org/D107919 GitOrigin-RevId: 2f1ee56f3cb8adb5aeadba3f66a8fc39fba1604d