Add infrastructure files to contrib

[Foxboron]

https://gitlab.archlinux.org/archlinux/infrastructure/-/tree/master/roles/archbuild/files

[jelly]

In my opinion clean-chroots related should go into devtools, but it needs to be rewritten into bash instead of zsh. clean-dests has as a similar issue.

Related https://github.com/archlinux/devtools/issues/52

[Foxboron]

I realized I don't really know what the diff* stuff is about. I'm thinking mkpkg and gitpkg can be moved to contrib.

I think clean-chroots can be moved to devtools indeed.

[Antiz96]

From my understanding, this issue is outdated and can be closed right?

[christian-heusel]

No it's not, the assumption here is that these scripts would also be useful for more people 😊

[lahwaacz]

Are we talking about all files in https://gitlab.archlinux.org/archlinux/infrastructure/-/tree/master/roles/archbuild/files or just the scripts?