Though cURL has served us well since we launched Check Run Reporter, shelling out to bash can be tedious in CI systems with complex DSLs. We've added plugins for CI systems to make working with them more natural. Custom CI tools also let us do things like build in retries and set variables automatically from the build environment.
Since we use Buildkite ourselves, it was naturally the first integration we wrote. Head on over to the plugin's GitHub repo for instructions.
Check out the repository for instructions. Note that the GitHub Actions run and uses steps have different working directories (since uses steps get mounted into a docker container), so you may need to experiment a bit to set the correct CHECK_RUN_REPORTER_ROOT value.