dont use import to determine if export onnx interface (#4801)

* dont use import to determine if export onnx

* fix

Co-authored-by: oneflow-ci-bot <69100618+oneflow-ci-bot@users.noreply.github.com>

tools/generate_oneflow_symbols_export_file.py

@@ -3,6 +3,8 @@ import sys
 import os
 import re
 import importlib
+import platform
+
 
 project_source_dir = sys.argv[1]
 python_dir = project_source_dir + "/oneflow/python"
@@ -39,9 +41,7 @@ for py_script in RecursiveFindPythonFile(python_dir):
 
 python_scripts = "from __future__ import absolute_import\n"
 for filepath in import_filepaths:
-    if "onnx" in filepath:
-        onnx = importlib.util.find_spec("onnx")
-        if onnx is None:
-            continue
+    if "onnx" in filepath and platform.system() == "Darwin":
+        continue
     python_scripts += "import oneflow.python.%s\n" % GetImportPath(filepath)
 open(output_filepath, "w").write(python_scripts)