cmake HAVE_ATOMIC_OPS_H examples

pingcap/tiflash contrib/libunwind-cmake/CMakeLists.txt :141 

find_file (HAVE_ATOMIC_OPS_H "atomic_ops.h")

ByConity/ByConity contrib/libunwind-old-cmake/CMakeLists.txt :164 

find_file (HAVE_ATOMIC_OPS_H "atomic_ops.h")