fix symlink

Author: suchenzang

metaseq/checkpoint_utils.py

@@ -100,8 +100,10 @@ def save_checkpoint(
         if len(checkpoints) > 1:
             # Create symlink between identical checkpoints (differing in naming for epoch/update/last).
             for other_checkpoint in checkpoints[1:]:
+                if PathManager.islink(other_checkpoint):
+                    PathManager.rm(other_checkpoint)
                 assert PathManager.symlink(
-                    checkpoints[0], other_checkpoint, overwrite=True
+                    checkpoints[0], other_checkpoint
                 ), f"Failed to symlink {checkpoints[0]} to {other_checkpoint}"
 
         write_timer.stop()