workflows: Add workaround for actions/checkout tag breakage

See https://github.com/actions/checkout/pull/697

.github/workflows/release.yml

@@ -11,6 +11,9 @@ jobs:
       - name: Clone repository
         uses: actions/checkout@v2
 
+      - name: Workaround for https://github.com/actions/checkout/pull/697
+        run: git fetch --force origin $(git describe --tags):refs/tags/$(git describe --tags)
+
       - name: Build release tarball
         # run as root; current Ubuntu podman breaks user networking ("could not find slirp4netns")
         run: sudo PUBLISH_TAR=1 tests/run-apt