Setup GHA self-hosted runner

[idigs]

GHA runner shall reside within the mantid-development based image, just like jenkins-agent.

[idigs]

@thomashampson has already solved the runner registration problem. see main...github-runner#diff-ad94a6c088570fcf6bb16fa639418aef5603f1f2efa4b2da8f97032f612eadda

REG_TOKEN=$(curl -L \
  -X POST \
  -H "Accept: application/vnd.github+json" \
  -H "Authorization: Bearer ${GITHUB_TOKEN}" \
  -H "X-GitHub-Api-Version: 2022-11-28" \
  https://api.github.com/repos/${ORGANIZATION}/${REPOSITORY}/actions/runners/registration-token \
  | jq .token --raw-output)

cd /home/docker/actions-runner

./config.sh --url https://github.com/${ORGANIZATION}/${REPOSITORY} --token ${REG_TOKEN}

The org-level token "GITHUB_TOKEN" is used to request a runner registration token. The registration token is one-time use only and once issued is used for registering a new runner.

[idigs]

mantidproject/mantid@main...thomashampson:mantid_github_actions_test:main

[idigs]

https://docs.github.com/en/rest/actions/self-hosted-runners?apiVersion=2022-11-28#create-a-registration-token-for-an-organization--fine-grained-access-tokens