Fix run-tests.sh when macos has gnu xargs
Fix run-tests.sh when macos has gnu xargs

UCEAP-IT/drupal-vm,debugacademy/drupal-vm,geerlingguy/drupal-vm,geerlingguy/drupal-vm,akeemw/drupal-vm,UCEAP-IT/drupal-vm,kentr/drupal-vm,kentr/drupal-vm,Luciditi/drupal-vm,akeemw/drupal-vm,kentr/drupal-vm,Luciditi/drupal-vm,debugacademy/drupal-vm,debugacademy/drupal-vm,joestewart/drupal-vm,akeemw/drupal-vm,debugacademy/drupal-vm,kentr/drupal-vm,kentr/drupal-vm,UCEAP-IT/drupal-vm,akeemw/drupal-vm,geerlingguy/drupal-vm,geerlingguy/drupal-vm,Luciditi/drupal-vm,joestewart/drupal-vm,joestewart/drupal-vm