fix delete all checkpoints when save_total_limit is set to 1 (#25136)

src/transformers/trainer.py

@@ -1960,7 +1960,7 @@ class Trainer:
         # Delete the last checkpoint when save_total_limit=1 if it's different from the best checkpoint and process allowed to save.
         if self.args.should_save and self.state.best_model_checkpoint is not None and self.args.save_total_limit == 1:
             for checkpoint in checkpoints_sorted:
-                if checkpoint != self.state.best_model_checkpoint:
+                if not os.path.samefile(checkpoint, self.state.best_model_checkpoint):
                     logger.info(f"Deleting older checkpoint [{checkpoint}] due to args.save_total_limit")
                     shutil.rmtree(checkpoint)