Add some placeholders to the volume directories to try and fix erratic ownership changes

root/setup.sh

@@ -51,6 +51,7 @@ function main() {
   setup_service_podman
   setup_service_runner
   setup_gitlab_config
+  setup_volumes
 
   finalize_ownership
 }
@@ -153,9 +154,11 @@ function setup_user() {
 function setup_volumes() {
   # Host volume mount necessary for nested-podman to use overlayfs2 for container & volume storage.
   mkdir -p /home/podman/.local/share/containers
+  touch /home/podman/.local/share/containers/.placeholder
 
   # Nested-container's local container-cache volume mount, recommended by gitlab-runner docs.
   mkdir -p /cache
+  touch /cache/.placeholder
 
   # Both the gitlab-runner and podman need access to the cache directory / volume mount.
   chown podman:runner /cache