Link CI build output to source code

Description including problem, use cases, benefits, and/or goals

When a build or test fails, there's usually log output that includes a reference to a file and line number. We should watch for those references and turn them into links that point to the GitLab file viewer using the correct branch and commit.

Proposal

Links / references

• https://developer.atlassian.com/blog/2016/06/hyperlinking-logs-to-source-code/