message: Fix build on old Apple Clang versions.
diff: @@ -162,7 +162,9 @@ inline uint64_t rotateleft64(uint64_t v, int x)
  {
  #if defined(_MSC_VER) && !defined(__clang__)
  return _rotl64(v, x);
  -#elif defined(__clang__) && __clang_major__ >= 8
  +// Apple's Clang 8 is actually vanilla Clang 3.9, there we need to look for
  +// version 11 instead: https://en.wikipedia.org/wiki/Xcode#Toolchain_versions
  +#elif defined(__clang__) && ((!defined(__apple_build_version__) && __clang_major__ >= 8) || __clang_major__ >= 11)
  return __builtin_rotateleft64(v, x);
  #else
  return (v << (x & 63)) | (v >> ((64 - x) & 63));
  