OCI recipe builds failing due to branch scalability issue

[Cristovao Cordeiro]

Affected OCI projects:
 - https://launchpad.net/cloud-images/+oci/ubuntu-base

Examples of failed builds:
 - https://launchpadlibrarian.net/731626207/buildlog_oci_ubuntu_focal_amd64_24.10_CANCELLING.txt.gz
 - https://launchpadlibrarian.net/731625937/buildlog_oci_ubuntu_focal_s390x_24.10_BUILDING.txt.gz

After investigating it with the LP team, we've noticed that the OCI builds are being executed with

 > git clone -n --depth 1 --no-single-branch ...

which raises a scalability issue, especially for this project (since the branches are quite chunky by default).

Looking at https://git.launchpad.net/launchpad-buildd/tree/lpbuildd/target/vcs.py#n93, we can see that (at least for the OCI builds) the flow is that we will `checkout` a single branch anyway, thus making the use of --no-single-branch unnecessary).

[Cristovao Cordeiro (cjdc)]

Update: I'm raising awareness on this bug as we haven't been able to build Ubuntu base images for some time now:
 - https://launchpad.net/~cloud-images-release-managers/cloud-images/+oci/ubuntu-base/+recipe/24.10
 - https://launchpad.net/~cloud-images-release-managers/cloud-images/+oci/ubuntu-base/+recipe/22.04
 - https://launchpad.net/~cloud-images-release-managers/cloud-images/+oci/ubuntu-base/+recipe/20.04