Use %setup macros for containerd.

[Romain-Geissler-1A]

This is a pre-requisite for building a containerd package for Fedora 45.

As discussed in #524.

[Romain-Geissler-1A]

In this version we totally ignore the %source content, and we build from /go/src. We did "a bit" that before as well. In other packages like docker-cli we seem to remove partially the content of /go/src to replace it by the content of the %source. Not sure what you want exactly. I guess we really want to build in /go/src to have stable builds and debug symbols that contain a fixed /go/src path ?

I can change that if you prefer another direction.

[vvoland]

I think the main reason wasn't for path consistent, but for the Git metadata present in /go/src. Probably for runc version?

But using the source from %setup would be more idiomatic and I think that's what we actually do for the other packages?

[Romain-Geissler-1A]

Ok @vvoland I also stopped using the checked out source files with the .git folders, now we use only the %sourceN plus the gen-ver rpm defines (I had to add one for the runc commit). It's ready for review.