User our own fork of ansi-test
We currently clone the https://gitlab.common-lisp.net/ansi-test/ansi-test when running CI. This means we also need to update the upstream version when we need to change our expected failures. This is already on a branch so we don't mess up the upstream version's master branch.
Instead, it seems better if we clone a copy and manage our own, periodically updating from the upstream version.
- Fork a copy of ansi-test to the cmucl group
- Update CI to use this version