Rebase on upstream, update to v0.21.0

Although we don't really need anything but Zola in this image, we can't
use the upstream image directly in a Jenkins job because it doesn't
contain a shell or any other utility that can "pause" the container.
Therefore, we do need to install the `pause` command, but we don't need
anything else from the _rsync_ image.

Containerfile

@@ -1,7 +1,5 @@
-FROM git.pyrocufflink.net/containerimages/rsync
+FROM ghcr.io/getzola/zola:v0.21.0
 
-COPY --from=ghcr.io/getzola/zola:v0.16.1 /bin/zola /usr/local/bin/zola
+COPY --from=registry.k8s.io/pause:3.9 /pause /bin/pause
 
-USER jenkins
-
-CMD ["/bin/python3", "-c", "import signal; signal.pause()"]
+ENTRYPOINT ["zola"]

Jenkinsfile

@@ -1 +1 @@
-buildContainerImage()
+buildContainerImage2(archlist: ["amd64","arm64"])