Civibuild Vagrant - drupal-case build?
Update: BuildKit currently cannot build Drupal 8 sites because of the composer requirement.

To build a Drupal 8 Clean site with CiviBuild you would use the command:

Note: CiviBuild cannot currently build Drupal 8 sites with the demo data.

civibuild create d8-master or civibuild create &lt;NAME&gt; --type drupal8-clean

Note: This will create a Civi 'master' site using the latest bleeding edge CiviCRM code. To build using a specific CiviCRM version use --civi-ver e.g. --civi-ver 5.6.0

The full command to create a Drupal 8, CiviCRM 5.6.0 without demo data and named d8c560 with the URL http://d8c560.test is:

civibuild create d8c560 --type drupal8-clean --civi-ver 5.6.0 --url http://d8c560.test

The build you refer to dcase or ==type drupal-case builds a Drupal 7 site for testing the CiviCase v5 extension.

CiviBuild Docs

The CiviBuild documentation is worth reading:
https://docs.civicrm.org/dev/en/latest/tools/civibuild/#build-types

CiviCase v5

Information on CiviCase v5 (it's awesome!) and the associated dcase build is here:
https://github.com/civicrm/org.civicrm.civicase