This happen in drupal 8.4.x

Status: Just wait drupal new release to solve this problem..

Read:

• https://www.drupal.org/docs/8/system-requirements/limitations-of-32-bit-php
• https://www.drupal.org/node/2795489
• https://api.drupal.org/api/drupal/core%21modules%21system%21system.install/function/system_requirements/8.4.x
• https://www.drupal.org/node/2860500
• https://github.com/symfony/symfony/issues/5227
• https://drupal.stackexchange.com/questions/238896/fresh-drupal-install-shows-drupal-core-warning