Generalize osmet-pack and use it for miniso packing

[jlebon]

The first commits work towards generalizing osmet-pack to support just running the matched coreos-installer in a supermin VM. The final patch makes the miniso packing step use it. Its commit message follows.

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cmd-buildextend-live: pack miniso with composed coreos-installer

Currently, we're packing the miniso using the coreos-installer from the cosa image. This is not ideal however, because it introduces skew between the packing side and the unpacking side, which may be older.

Fix this by using the new runvm-coreos-installer to pack with the composed coreos-installer.

For more information, see: https://github.com/coreos/coreos-assembler/pull/3009

[bgilbert]

Looks like osmet packing is unhappy in CI.

[cgwalters]

OK I'm just discovering that we need this in order to use newer coreos-installer to build older RHCOS, e.g 4.10.

I'm worried this is actually a symptom of a bigger picture problem in that the rhcos-4.11 style branches are basically a lie because the Fedora repos keep floating forward.

I think I'd say we actually pin the versions of key tools used in this repository as a general rule - and that includes e.g. rpm-ostree where I think we also may have removed or changed experimental/hidden features that are depended on by older coreos-assembler branches. And we haven't noticed because we haven't been rebuilding containers for older branches often.

EDIT: Sorry I see https://github.com/coreos/coreos-assembler/commit/ca2dbcca1d0b10c8fdb6e54cdc46903865920573

[jlebon]

OK, I think this is finally ready to go now!

[jlebon]

/retest

[jlebon]

Prow failing on https://github.com/openshift/os/issues/1028. /override ci/prow/rhcos

Let's merge this once FCOS releases are done this week.

[openshift-ci[bot]]

@jlebon: Overrode contexts on behalf of jlebon: ci/prow/rhcos

In response to this:

Prow failing on https://github.com/openshift/os/issues/1028. /override ci/prow/rhcos

Let's merge this once FCOS releases are done this week.

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