Add Fedora 45. - #513

Thanks, can you rebase the PR? CI should be good now!

Ugh looks like we need another rebase after merging #510

I have added the --nosignature flag to cope with rpm 6 (and updated the commit message to explain why). We are down to 2 failures, both on fedora 45. Somehow the containerd package doesn't build fine on fedora 45 and from the log I don't really get what's the problem to be honest...

Wondering if it's this part; something expects a rpmbuild.env file to be generated / present;

#37 0.894 Executing(%build): /bin/sh -e /var/tmp/rpm-tmp.Trgqb5
#37 0.896 /var/tmp/rpm-tmp.Trgqb5: line 3: /root/rpmbuild/BUILD/containerd.io-0.0.0_20260911171230_ebd19f0-build/rpmbuild.env: No such file or directory
#37 0.896 error: Bad exit status from /var/tmp/rpm-tmp.Trgqb5 (%build)
#37 0.897     line 38: It's not recommended to have unversioned Obsoletes: Obsoletes: containerd
#37 0.897     line 39: It's not recommended to have unversioned Obsoletes: Obsoletes: runc
#37 0.897     Bad exit status from /var/tmp/rpm-tmp.Trgqb5 (%build)

In the end it required 2 distinct pre-requisite fixes that you can review separately before considering this pull request:

• Disable rpm signature check (for local testing). #523
• Keep containerd's rpmbuild.env if it exists. #524 which honestly seems more like a hack than a "good fix", but... it was like this before. Hopefully we can find on the long term a better solution than what I propose in this pull request.

Ugh, I meant to approve and merge #513, but this one is fine now too 😅