[ci] workaround for some podman/systemd issue

.gitlab-ci.yml

@@ -7,8 +7,8 @@ build ubuntu:
   tags: [linux, shell]
   script:
     - image_name="${CI_REGISTRY}/${CI_PROJECT_PATH,,}"
-    - podman build --pull -t "${image_name}/ubuntu" ubuntu
-    - podman build -t "${image_name}/jupyterhub" jupyterhub
+    - podman build --cgroup-manager=cgroupfs --pull -t "${image_name}/ubuntu" ubuntu
+    - podman build --cgroup-manager=cgroupfs -t "${image_name}/jupyterhub" jupyterhub
 
 deploy ubuntu:
   stage: deploy