contrib: fxc2: fix call under wine

Otherwise we get this error:

  File "/builds/robUx4/vlc/contrib/i686-w64-mingw32/bin/fxc", line 27, in toSystemPath
    sub = subprocess.Popen([pathCmd, '-m', absPath], shell=False, stderr=subprocess.DEVNULL, stdout=subprocess.PIPE)
          ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/usr/lib/python3.11/subprocess.py", line 1024, in __init__
    self._execute_child(args, executable, preexec_fn, close_fds,
  File "/usr/lib/python3.11/subprocess.py", line 1901, in _execute_child
    raise child_exception_type(errno_num, err_msg, err_filename)
FileNotFoundError: [Errno 2] No such file or directory: 'wine winepath'