We have accidentally introduced a BC break in Sulu 1.6.9, while trying to fix some regressions from Symfony 3.4. Because of the way the new Symfony version handles the caching of the container, it is not possible anymore to execute any commands after clearing the cache.
Therefore we decided to remove the cache clearing step in the sulu:build command. However, this breaks other bundles like the ArticleBundle which are relying on this step.
The solution was to add this step again but simply do nothing when Symfony 3.4 is installed. That means that if you want to clear the cache before executing "sulu:build" you have to do that now manually.
This is the only fix that was released with Sulu 1.6.10.