docs: private static void _chmod(File f, int mask) throws IOException {
          // TODO WindowsPosix actually does something here (WindowsLibC._wchmod); should we let it?
          // Anyway the existing calls already skip this method if on Windows.
          if (File.pathSeparatorChar==';')  return; // noop
  
          if (Util.NATIVE_CHMOD_MODE) {
              PosixAPI.jnr().chmod(f.getAbsolutePath(), mask);
          } else {
              Files.setPosixFilePermissions(fileToPath(f), Util.modeToPermissions(mask));
          }
      }