fix onnx export bug

hnluo

2023-08-29 72b6c7735e44fff12c4a3d401deb98c59f16ab0f

 funasr/build_utils/build_args.py

@@ -54,6 +54,12 @@
            default=None,
            help="The number of input dimension of the feature",
        )
        task_parser.add_argument(
            "--cmvn_file",
            type=str_or_none,
            default=None,
            help="The path of cmvn file.",
        )

    elif args.task_name == "lm":
        from funasr.build_utils.build_lm_model import class_choices_list