stream_layered_image: Add main method

pkgs/build-support/docker/stream_layered_image.py

@@ -181,8 +181,7 @@ def add_bytes(tar, path, content, mtime):
     tar.addfile(ti, io.BytesIO(content))
 
 
-# Main
-
+def main():
     with open(sys.argv[1], "r") as f:
         conf = json.load(f)
 
@@ -248,3 +247,7 @@ with tarfile.open(mode="w|", fileobj=sys.stdout.buffer) as tar:
         add_bytes(tar, "manifest.json", manifest_json, mtime=mtime)
 
         print("Done.", file=sys.stderr)
+
+
+if __name__ == "__main__":
+    main()