Enable arm64 runtime smoke execution

.gitea/workflows/runtime-distribution.yml

@@ -39,6 +39,10 @@ on:
         description: Digest-pinned GreenMail image
         required: true
         type: string
+      binfmt_image:
+        description: Digest-pinned tonistiigi/binfmt image for arm64 CI execution
+        required: true
+        type: string
 
 jobs:
   publish-runtime:
@@ -64,6 +68,7 @@ jobs:
           MANAGED_INGRESS_IMAGE: ${{ inputs.managed_ingress_image }}
           GARAGE_IMAGE: ${{ inputs.garage_image }}
           TEST_MAIL_IMAGE: ${{ inputs.test_mail_image }}
+          BINFMT_IMAGE: ${{ inputs.binfmt_image }}
         run: |
           python - <<'PY'
           import os
@@ -82,6 +87,7 @@ jobs:
               "MANAGED_INGRESS_IMAGE",
               "GARAGE_IMAGE",
               "TEST_MAIL_IMAGE",
+              "BINFMT_IMAGE",
           ):
               if image_pattern.fullmatch(os.environ[name]) is None:
                   raise SystemExit(f"{name} must be an exact sha256 image reference")
@@ -213,6 +219,11 @@ jobs:
             --index-digest "${REDIS_IMAGE##*@}" \
             --index runtime-output/redis-index.json \
             --output runtime-output/redis-metadata.json
+      - name: Register arm64 execution for runtime smoke
+        working-directory: govoplan
+        env:
+          BINFMT_IMAGE: ${{ inputs.binfmt_image }}
+        run: docker run --privileged --rm "$BINFMT_IMAGE" --install arm64
       - name: Exercise amd64 and arm64 runtime images
         working-directory: govoplan
         run: |