ci: Force running FreeBSD build in tag and push pipelines

This now behaves similar to other CI build jobs, which always run on the
main branches, but only conditionally on PRs, depending on which files
changed.

.cirrus.yml

@@ -9,6 +9,7 @@ build_task:
   # Github Actions build workflow will run on those and the
   # "Fetch from FreeBSD" job should not fail.
   only_if: |
+    $CIRRUS_TAG != '' || $CIRRUS_BRANCH == 'main' || $CIRRUS_BRANCH =~ 'v*' ||
     changesInclude(
       '.github/workflows/build.yaml',
       '.github/actions/setup-nix/**',