Detect atomic operations support on ppc64le
On powerpc64le are normal atomic operations undetected, because powerpc64le-* is not supported in configure. It makes platform.h header different. If standard atomic operations are unavailable (like on CentOS 7), it would not detect any atomic operations, unlike ppc64 and ppc platform.
Affects only ~"v9.11"
arch=ppc64le, build system type == "powerpc64le-unknown-linux-gnu" on RHEL 8