mf.dll is a symlink

[HughPH]

lrwxrwxrwx 1 hugh hugh      76 Dec  5 23:58 mf.dll -> /home/hugh/.steam/compatibilitytools.d/Proton-5.21-GE-1/dist/lib/wine/mf.dll

The upshot is that it cannot be modified and I get a Permission denied error:

$ WINEPREFIX=/mnt/f/steamapps/compatdata/397540/pfx ./install-mf-64.sh 
mediafoundation
- wow64_microsoft-windows-mediafoundation_31bf3856ad364e35_6.1.7601.17514_none_04d9defd57c1f6bf.manifest (wow64)
- amd64_microsoft-windows-mediafoundation_31bf3856ad364e35_6.1.7601.17514_none_fa8534ab236134c4.manifest (win64)
- mf.dll -> /mnt/f/steamapps/compatdata/397540/pfx/drive_c/windows/syswow64
Traceback (most recent call last):
  File "installcab.py", line 319, in <module>
    process_files(output_files)
  File "installcab.py", line 257, in process_files
    install_dll(file_path)
  File "installcab.py", line 231, in install_dll
    shutil.copy(dll_path, dest_dir)
  File "/usr/lib/python2.7/shutil.py", line 139, in copy
    copyfile(src, dst)
  File "/usr/lib/python2.7/shutil.py", line 97, in copyfile
    with open(dst, 'wb') as fdst:
IOError: [Errno 13] Permission denied: '/mnt/f/steamapps/compatdata/397540/pfx/drive_c/windows/syswow64/mf.dll'