The type of platformFormat for Rules is conditionally selected at
compilation time. As such it is only intended for direct use with external OS
functions and code that expects platformFormat to be stable across platforms
may fail to subsequently compile on a differing platform.
For example: on Windows or OSX platformFormat will be Text,
and on Linux it will be ByteString.
If portability is a concern, restrict usage to functions which do not expose
platformFormat directly.