It is not possible to build containers using Buildah in unprivileged mode

1. Deploy an Openshift cluster
2. Deploy Tekton pipelines using the Redhat operator
3. Follow the instructions to build a Dockerfile: https://docs.openshift.com/container-platform/4.10/cicd/pipelines/unprivileged-building-of-container-images-using-buildah.html 

The pipeline fails at the buildah stage, before the step scripts runs, with the following error:

STEP-BUILDtime="2023-05-22T17:08:02Z" level=warning msg="error running newgidmap: exit status 1: newgidmap: write to gid_map failed: Operation not permitted\n"
time="2023-05-22T17:08:02Z" level=warning msg="falling back to single mapping"
time="2023-05-22T17:08:02Z" level=warning msg="error running newuidmap: exit status 1: newuidmap: write to uid_map failed: Operation not permitted\n"
time="2023-05-22T17:08:02Z" level=warning msg="falling back to single mapping"
'overlay' is not supported over overlayfs, a mount_program is required: backing file system is unsupported for this graph driver
time="2023-05-22T17:08:02Z" level=warning msg="failed to shutdown storage: \"'overlay' is not supported over overlayfs, a mount_program is required: backing file system is unsupported for this graph driver\""
time="2023-05-22T17:08:02Z" level=error msg="exit status 125"