ci: Ensure composefs is enabled on Fedora

[cgwalters]

For some reason we're not picking this up in the Prow build, which breaks things because now rpm-ostree hard requires it.

Let's make this a fatal build time error for more clear debugging.

[cgwalters]

OK now we're hitting

Oct 06 17:37:04 ostree-prepare-root[559]: Loading etc/ostree/prepare-root.conf
Oct 06 17:37:04 systemd[1]: Starting ostree-prepare-root.service - OSTree Prepare OS/...
Oct 06 17:37:04 ostree-prepare-root[559]: Resolved OSTree target to: /sysroot/ostree/deploy/fedora-coreos/deploy/e941f5f8527ed75bed251cbf74826f6eaf77e076c7a2d57858859dd22f3bade1.0
Oct 06 17:37:04 ostree-prepare-root[559]: sysroot.readonly configuration value: 1 (fs writable: 1)
Oct 06 17:37:04 ostree-prepare-root[559]: composefs+ostree: Validated commit signature using '/etc/ostree/initramfs-root-binding.key'
Oct 06 17:37:04 ostree-prepare-root[559]: ostree-prepare-root: Signature validation requested, but no valid digest in commit
Oct 06 17:37:04 systemd[1]: �[0;1;39m�[0;1;31m�[0;1;39mostree-prepare-root.service: Main process exited, code=exited, status=1/FAILURE�[0m
Oct 06 17:37:04 systemd[1]: �[0;1;38;5;185m�[0;1;39m�[0;1;38;5;185mostree-prepare-root.service: Failed with result 'exit-code'.�[0m
Oct 06 17:37:04 systemd[1]: �[0;1;31m�[0;1;39m�[0;1;31mFailed to start ostree-prepare-root.service - OSTree Prepare OS/.�[0m
Oct 06 17:37:04 systemd[1]: ostree-prepare-root.service: Triggering OnFailure= dependencies.

hmm...thinking this is some sort of drift w/rpm-ostree. Need to dig in

[cgwalters]

Right we need rpm-ostree v2023.8 which enables composefs client side for this, but now I'm confused how it worked before?

[alexlarsson]

Oh, I wonder if this is the issue @ericcurtin hit, where somehow the default to enable composefs was disabled in the fedora packages after a new release? I forgot the details about that though...

[cgwalters]

/retest

[ericcurtin]

I think #3071 is related

[cgwalters]

OK now we're getting:

Oct 10 16:37:46 ostree-prepare-root[559]: composefs: Verifying digest: 6d5afb6a78a5487576ff00aa993693d01fd01d73e50c382a67eb1db6f5db9fcc
Oct 10 16:37:46 ostree-prepare-root[559]: ostree-prepare-root: composefs: failed to mount: fsverity not enabled on composefs image

which is good actually but yes, to make this test really work we currently need to either eat the hit and reprovision to ext4 on boot with ignition or use !coreos.

[jlebon]

Looks sane to me.