fix test device spec relative path importing issue (#37190)

Signed-off-by: YAO Matrix <matrix.yao@intel.com>
Co-authored-by: Yih-Dar <2521628+ydshieh@users.noreply.github.com>

Author: yao-matrix

src/transformers/testing_utils.py

@@ -3005,6 +3005,8 @@ def backend_device_count(device: str):
 
         # Try to strip extension for later import – also verifies we are importing a
         # python file.
+        device_spec_dir, _ = os.path.split(os.path.realpath(device_spec_path))
+        sys.path.append(device_spec_dir)
         try:
             import_name = device_spec_path[: device_spec_path.index(".py")]
         except ValueError as e: