Aarch64 Binaries Now Require ARMv8.2 with Added CMake Option for ARMv8.0 Compatibility

Aarch64 binaries now require at least ARMv8.2, released in 2016. Most notably, this enables use of ARM LSE, i.e. native atomic operations. Also, CMake build option "NO_ARMV81_OR_HIGHER" has been added to allow compilation of binaries for older ARMv8.0 hardware, e.g. Raspberry Pi 4. #41610 (Robert Schulze).