[clang] [llvm] Ci plugin (PR #113290)

[David Spickett via cfe-commits]

DavidSpickett wrote:

Abandoning this, as confirmed by https://discourse.llvm.org/t/using-plugins-in-buildkite-ci-that-require-docker/82701/3?u=davidspickett we cannot run docker on our Linux instances without a lot of hassle. Plus, the plugin authors do not want to support running without docker.

I will start on a script to generate reports instead.

https://github.com/llvm/llvm-project/pull/113290