Fix importing transformers on Windows (#4997)

src/transformers/benchmark/benchmark_utils.py

@@ -16,7 +16,6 @@ from collections import defaultdict, namedtuple
 from datetime import datetime
 from multiprocessing import Pipe, Process
 from multiprocessing.connection import Connection
-from signal import SIGKILL
 from typing import Callable, Iterable, List, NamedTuple, Optional, Union
 
 from transformers import AutoConfig, PretrainedConfig
@@ -33,6 +32,12 @@ if is_tf_available():
     from tensorflow.python.eager import context as tf_context
 
 
+if platform.system() == "Windows":
+    from signal import CTRL_C_EVENT as SIGKILL
+else:
+    from signal import SIGKILL
+
+
 logger = logging.getLogger(__name__)  # pylint: disable=invalid-name