[squad] add version tag to squad cache (#5669)

src/transformers/data/datasets/squad.py

@@ -113,9 +113,12 @@ class SquadDataset(Dataset):
                 raise KeyError("mode is not a valid split name")
         self.mode = mode
         # Load data features from cache or dataset file
+        version_tag = "v2" if args.version_2_with_negative else "v1"
         cached_features_file = os.path.join(
             cache_dir if cache_dir is not None else args.data_dir,
-            "cached_{}_{}_{}".format(mode.value, tokenizer.__class__.__name__, str(args.max_seq_length),),
+            "cached_{}_{}_{}_{}".format(
+                mode.value, tokenizer.__class__.__name__, str(args.max_seq_length), version_tag,
+            ),
         )
 
         # Make sure only the first process in distributed training processes the dataset,