v1.2.0

Bump pkgproxy from v0.8.0 to v0.11.0, and save the package cache in a form pkgproxy 0.12 will need.

• pkgproxy 0.9–0.11: LXD 6.10+ image registries for setup lxd-remote, offline modes (pkgproxyctl offline, and going offline with the machine's network), setup rockcraft / setup charmcraft, and setup status. Setup scripts now fail when they can't set up their tool, instead of silently doing nothing.
• The package cache is saved as an archive that keeps extended attributes. pkgproxy 0.12 will store each cached file's metadata in an xattr, and the tar inside actions/cache drops xattrs. When pkgproxy stops, its unit now writes /var/cache/pkgproxy-archive/cache.tar with tar --xattrs, and the cache-dir output points at that directory. Your save steps don't change, as long as they stop pkgproxy before saving, as the README has always shown.
• package-cache-key default is now pkgproxy-cache-v4: it's a new cache format, so the first run after upgrading starts cold on each CPU arch.
• README:
  • how to give the runner user LXD access on GitHub-hosted runners (usermod plus sg lxd);
  • the snapcraft hook check updated for pkgproxy 0.11's inline hooks;
  • the manual snapcraft project pre-creation step removed, because setup snapcraft now creates the project.
• CI builds a real snap through pkgproxy on ubuntu-22.04, 24.04 and 24.04-arm, and checks that the saved cache comes back with its xattrs.

v2.0.0 is out alongside this release: it saves the cache itself at the end of the job. See its notes for how to upgrade.