title: --global option does not exist while doing a composer --global require
body: <p>I'm trying to set up my work environment at home. I'm developing a drupal8 project and need to run with a vagrant. So far so good, installed of vagrant composer and php went well. Now I need to use drush to be able to rebuild my cache etc.</p>
  
  <p>Here some more infos :</p>
  
  <pre><code>vagrant@lashootingboxd8:/var/www/drupalvm/drupal$ composer --version
  Composer version 1.9.0 2019-08-02 20:55:32
  </code></pre>
  
  <pre><code>vagrant@lashootingboxd8:/var/www/drupalvm/drupal$ composer --global require drush/drush
      1/1:        https://packages.drupal.org/8/drupal/provider-2019-3$3852c4e111957318dd45daf9d2d7b3ab725e924276f9288a039edfea6e7a8e56.json
      Finished: success: 1, skipped: 0, failure: 0, total: 1
      1/2:        http://repo.packagist.org/p/provider-latest$febfbf81e3ff08dabc4f583cddc865afb94c4c6c978e23baa7372527f0cbdf3a.json
      2/2:        http://repo.packagist.org/p/provider-2019-07$b9d9f8cb7e5d9896a78be68dec5d2d9e7ec04a5e5cc4d500f799d4cb8af75e4a.json
      Finished: success: 2, skipped: 0, failure: 0, total: 2
  
  
    [Symfony\Component\Console\Exception\RuntimeException]  
    The "--global" option does not exist
  </code></pre>
  
  <p>So if you guys have any idea of how to fix that would be awesome</p>
  
  <p>EDIT : 
  I did try the composer gloab require drush/drush, it doesn't give me an error but I still don't have anything as you can see below : (sorry I'm a very very noobie for this type of problem)
  <a href="https://i.stack.imgur.com/vOZKE.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/vOZKE.png" alt="enter image description here"></a></p>