build-sys: Hard require libostree 2020.1

[cgwalters]

The current rpm-ostree-2020.1-1.fc31.x86_64 in Fedora
was built with a truly ancient libostree
because Fedora's build system is weird and only adds packages
released after "gold" into the buildroot via an override
that times out.

This actively breaks things because rpm-ostree isn't
detecting the read-only sysroot.

Let's bump our hard requirement.

[jlebon]

/lgtm

I took the liberty of pushing another commit here so that we stop using FAHC, which was causing us to still pull in old libostree and break compilation.

If you have review comments on that commit, feel free to /hold it!

[cgwalters]

OK we have a deadlock now:

Resolving dependencies... done
error: Could not depsolve transaction; 1 problem detected:
 Problem: package rpm-ostree-2020.1.37.g11bc82ea-1.fc31.x86_64 requires libostree-1.so.1(LIBOSTREE_2020.1)(64bit), but none of the providers can be installed
  - conflicting requests
  - package ostree-libs-2020.2-2.fc31.x86_64 is filtered out by exclude filtering

Hmm. OK so we can probably unbreak this by overriding ostree in this repo.

[jlebon]

/lgtm

[openshift-ci-robot]

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[openshift-ci-robot]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: cgwalters, jlebon

The full list of commands accepted by this bot can be found here.

The pull request process is described here

Needs approval from an approver in each of these files:

• OWNERS [cgwalters,jlebon]

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[jlebon]

OK cool, this is now hitting EROFS, which is a good sign because it means that it's actually using the latest libostree. So we'll need ostreedev/ostree#2027 first.

[cgwalters]

/override continuous-integration/jenkins/pr-merge
because we know this is good. Now just needs a lgtm.

[openshift-ci-robot]

@cgwalters: Overrode contexts on behalf of cgwalters: continuous-integration/jenkins/pr-merge

In response to this:

/override continuous-integration/jenkins/pr-merge
because we know this is good. Now just needs a lgtm.

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