How can I fetch a commit message in AWS CodePipeline/CodeBuild to implement a `[skip ci]` command?

I’m using an AWS CodePipeline with GitHub Connections as the source action to deploy a Python app to an AWS Elastic BeanStalk. I’d like to emulate GitHub Actions’ [skip ci] feature by detecting a commit message prefix and exiting early if present, canceling the build stage. I found this post, but the commented solution doesn’t work with GitHub connections as the source of the action.