Update build_updatexml.yml

.github/workflows/build_updatexml.yml

@@ -110,7 +110,8 @@ jobs:
         run: |
           set -euo pipefail
 
-          python3 -c $'import os
+          python3 - <<'PY'
+          import os
           import xml.etree.ElementTree as ET
           from pathlib import Path
 
@@ -144,7 +145,7 @@ out_path.parent.mkdir(parents=True, exist_ok=True)
           tree.write(out_path, encoding="utf-8", xml_declaration=True)
 
           print(f"Wrote: {out_path}")
-'
+          PY
 
       - name: Attach updates.xml to GitHub Release
         if: ${{ github.event_name == 'release' || github.event.inputs.release_tag != '' }}