Drop (non functional) windows support

[leucos]

Windows support is quite some work (.exe everywhere, no real symlinks, no executable replacing, different compression format for many distributions...) for a non-existent user base.

We are not willing to spend time for this platform. If anyone is willing to do it; please go ahead.

Otherwise, we'll remove windows-related stuff (.exe templating, windows speficics in distributions.yaml, cross-compilation) early 2021.

[Nex-Otaku]

Windows got now integrated Linux Subsystem: WSL 2.

It is really mature product.

As of moment, following Linux distributions are available in WSL 2:

Ubuntu 16.04 LTS
Ubuntu 18.04 LTS
Ubuntu 20.04 LTS (I am using it every day)
openSUSE Leap 15.1
SUSE Linux Enterprise Server 12 SP5
SUSE Linux Enterprise Server 15 SP1
Kali Linux
Debian GNU/Linux
Fedora Remix for WSL
Pengwin
Pengwin Enterprise
Alpine WSL

So any user on Windows with WSL 2 enabled can run linux binaries with ease. Not really need for ".exe" files...