Windows nowadays has a tar.exe in System32 which is first in PATH
with a clean MSYS2 install.
This will both confuse users as well as scripts because it is
a non-cygwin bsdtar.
To avoid surprises add tar to base.
* Add a base package
This is meant as a replacement for the base group and contains the
same packages. If a user has the base package installed (the installer
will do this in the future) then we can add new packages to the base
and users with existing installations will get those packages installed
automatically.
This follows what Arch did last year:
https://www.archlinux.org/news/base-group-replaced-by-mandatory-base-package-manual-intervention-required/
See #1976
* base: explicitly depend on zstd and wget
They get already pulled in through pactoys, but this makes it explicit
