py2app "/usr/lib/libstdc++.6.dylib: No such file or directory" error

Question

When I was building LDOCE5 Viewer on macOS Big Sur with the command sudo DISTUTILS_DEBUG=1 python3 setup.py py2app, the output printed this error:

copying file /usr/lib/libstdc++.6.dylib -> /Users/armin/Projects/PythonProjects/ldoce5viewer-pyqt5/dist/LDOCE5 Viewer.app/Contents/Resources/qt_plugins/imageformats/usr/lib/libstdc++.6.dylib
error: [Errno 2] /usr/lib/libstdc++.6.dylib: 'No such file or directory'
Traceback (most recent call last):
  File "/Users/armin/Projects/PythonProjects/ldoce5viewer-pyqt5/setup.py", line 107, in <module>
    setup(
  File "/usr/local/Cellar/python@3.9/3.9.0_2/Frameworks/Python.framework/Versions/3.9/lib/python3.9/distutils/core.py", line 148, in setup
    dist.run_commands()
  File "/usr/local/Cellar/python@3.9/3.9.0_2/Frameworks/Python.framework/Versions/3.9/lib/python3.9/distutils/dist.py", line 966, in run_commands
    self.run_command(cmd)
  File "/usr/local/Cellar/python@3.9/3.9.0_2/Frameworks/Python.framework/Versions/3.9/lib/python3.9/distutils/dist.py", line 985, in run_command
    cmd_obj.run()
  File "/usr/local/lib/python3.9/site-packages/py2app/build_app.py", line 907, in run
    self._run()
  File "/usr/local/lib/python3.9/site-packages/py2app/build_app.py", line 1125, in _run
    self.run_normal()
  File "/usr/local/lib/python3.9/site-packages/py2app/build_app.py", line 1238, in run_normal
    self.create_binaries(py_files, pkgdirs, extensions, loader_files)
  File "/usr/local/lib/python3.9/site-packages/py2app/build_app.py", line 1545, in create_binaries
    dst = self.build_executable(
  File "/usr/local/lib/python3.9/site-packages/py2app/build_app.py", line 2367, in build_executable
    copy_resource(src, dest, dry_run=self.dry_run)
  File "/usr/local/lib/python3.9/site-packages/py2app/util.py", line 140, in copy_resource
    copy_resource(
  File "/usr/local/lib/python3.9/site-packages/py2app/util.py", line 140, in copy_resource
    copy_resource(
  File "/usr/local/lib/python3.9/site-packages/py2app/util.py", line 140, in copy_resource
    copy_resource(
  File "/usr/local/lib/python3.9/site-packages/py2app/util.py", line 153, in copy_resource
    copy_file(source, destination, dry_run=dry_run, preserve_mode=True)
  File "/usr/local/lib/python3.9/site-packages/py2app/util.py", line 166, in copy_file
    _copy_file(
  File "/usr/local/lib/python3.9/site-packages/py2app/util.py", line 191, in _copy_file
    with zipio.open(source, "rb") as fp_in:
  File "/usr/local/lib/python3.9/site-packages/modulegraph/zipio.py", line 84, in open
    path, rest = _locate(path)
  File "/usr/local/lib/python3.9/site-packages/modulegraph/zipio.py", line 68, in _locate
    raise IOError(_errno.ENOENT, full_path, "No such file or directory")
FileNotFoundError: [Errno 2] /usr/lib/libstdc++.6.dylib: 'No such file or directory'

This app uses PyQt5 and py2app with this setup.py, and I also installed these packages:

brew install pyqt gstreamer gst-plugins-base gst-plugins-good gst-plugins-ugly osxfuse gcc
pip3 install lxml pyobjc-core pyobjc-framework-Cocoa whoosh py2app

As far as I know, libstdc++.6 is deprecated but I can't find which module in this project is using it. So how can I fix this problem?