svm: fix check_libcontainer_annotations

Author: zapster

substratevm/mx.substratevm/mx_substratevm.py

@@ -2225,7 +2225,7 @@ def _get_libcontainer_files():
     libcontainer_project = mx.project("com.oracle.svm.native.libcontainer")
     libcontainer_dir = libcontainer_project.dir
     for src_dir in libcontainer_project.source_dirs():
-        for path, subdirs, files in os.walk(src_dir):
+        for path, _, files in os.walk(src_dir):
             for name in files:
                 abs_path = pathlib.PurePath(path, name)
                 rel_path = abs_path.relative_to(libcontainer_dir)