Matching the configuration used by the prospective FreeBSD CI runner.
In eca9196dc882 I added an abilist from my local development environment, but the configuration used by the CI bot is different.
With this abilist, and some additional work-in-progress changes, I have a green FreeBSD run: https://buildkite.com/llvm-project/libcxx-ci/builds/17075#01859d7d-2444-4152-a2e6-a4e41c3912fc