fix(#139): re-enable linux/arm64 podman builds

The failure was due to the kepler-pipglr gitlab runner which was in bad
state.

.gitlab-ci.yml

@@ -141,7 +141,7 @@ tests:
     - export MANIFEST=localhost/manifest-$IMAGE_NAME:$MILESTONE
     - echo $MANIFEST
     - podman manifest rm "$MANIFEST" 2>/dev/null || true
-    - podman build --layers --platform linux/amd64 --manifest "$MANIFEST" -f docker/Dockerfile $PODMAN_BUILD_OPTIONS .
+    - podman build --layers --platform linux/amd64,linux/arm64 --manifest "$MANIFEST" -f docker/Dockerfile $PODMAN_BUILD_OPTIONS .
     - podman manifest push --all "$MANIFEST" "docker://docker.io/$IMAGE_NAME:$MILESTONE"
     - podman manifest push --all "$MANIFEST" "docker://docker.io/$IMAGE_NAME:latest"
   after_script: