We use std::fs::canonicalize() and that may produce paths like
`\\\\?\\C:\\foobar\\baz.60`
where the leading `\?` disables all parsing.
When `baz.60` imports another `.60` file using a relative path `../fob.60`,
we call `Path::join()`, which really just appends strings, producing
``\\\\?\\C:\\foobar\\../fob.60`
When calling `canonicalize()` again on this path, the function fails,
because any parsing was disabled,
so neither the forward slash nor the .. are resolved.
So while the forward slash handling could be solved with `components()` we
still run into
https://users.rust-lang.org/t/unable-to-parse-relative-directories-in-windows-unc-paths/8164
To circumvent all this, use the dunce crate to canonicalize in a way on Windows
that avoids UNC paths.
