As `std::os::unix` is obviously not available on Windows, resort to the
`winpipe` crate, which implements a very similar API for named pipes.
Apart from simple changes to imports, we need to jump through a few
hoops because the `std::io::{Read, Write}` impls are on `&mut` for
`winpipe`, thus yielding different mutability requirements on Unix vs.
Windows.
We resort to cloning, but as this fallible, swallow the added complexity
of a platform-dependent implementation to not risk panics on Unix.
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