Resolve #3394413 "Basic pipeline"

Closes #3394413

The goal here is to add a basic pipeline that doesn't run any tests, but builds successfully. The goal is to have a core clone with the Automatic Updates and Package Manager modules converted to core modules.

.gitlab-ci.yml

@@ -121,3 +121,5 @@ composer:
     - composer install $COMPOSER_EXTRA
     - rm expand_composer_json.php
     - composer run core-convert --working-dir=./modules/contrib/automatic_updates -- $PWD --gitlabci
+    - ls -l ./core/modules/package_manager
+    - ls -l ./core/modules/auto_updates