Fix the Windows build

[Nonius]

At the core team nobody uses Windows as a development environment, so the Windows build is failing. Would be nice if somebody who uses Windows would fix the build for it.

[sagacity]

I built the current master of libunftp on my Windows 10 (version 20H2) and that worked fine, including tests. So perhaps it's something in the CI pipeline not going as expected?

[hannesdejager]

Good to hear. Does it run?

[sagacity]

I only compiled the lib. Is there a example binary I could try, or should I just build the unftp project as well?

[hannesdejager]

You could try running basic.rs in the examples directory.

[sagacity]

That works fine, I could connect via Filezilla and happily browse my temp folder.

[robklg]

According to @dani-garcia in #413 Windows is working 👍