cmake HAVE_LZCNT examples

GreatSQL/GreatSQL cmake/compiler_features.cmake :90

CHECK_CXX_SOURCE_RUNS("
#include <cstdint>
#include <immintrin.h>
int main(int argc, char *argv[]) {
  int a = (int)_lzcnt_u64((uint64_t)argc);
  return 0;
}
" HAVE_LZCNT)

GreatSQL/GreatSQL cmake/compiler_features.cmake :234

add_definitions(-DHAVE_LZCNT)