Image build is optimized.

.gitlab-ci.yml

@@ -31,6 +31,10 @@ before_script:
   - docker network prune -f || true
   - docker image prune -a -f || true
   - docker builder prune -f || true
+  - apt-get clean
+  - rm -rf /var/lib/apt/lists/*
+  - rm -rf /tmp/*
+  - journalctl --vacuum-time=1s
 
 after_script:
   - docker system prune -a -f --volumes || true