fix rmtree failure in coreml

Summary: Use actual temp directory  instead of local folder "tmp/" to avoid rmtree failure.

Differential Revision: D83371990

Author: YIWENX14

backends/apple/coreml/compiler/coreml_preprocess.py

@@ -11,6 +11,7 @@
 from enum import Enum
 
 from pathlib import Path
+import tempfile
 
 from typing import Any, Dict, final, List, Optional, Tuple
 
@@ -415,7 +416,7 @@ def preprocess_model(
         mlmodel: ct.models.MLModel, model_type: MODEL_TYPE
     ) -> PreprocessResult:
         identifier = "executorch_" + str(uuid.uuid4())
-        dir_path: Path = Path("tmp") / identifier
+        dir_path: Path = Path(tempfile.gettempdir()) / identifier
         model_dir_path: Path = dir_path / "lowered_module"
         model_spec: ct.proto.Model_pb2 = mlmodel.get_spec()
         logger.warning(