AWS CodeBuild: CODEBUILD_SOURCE_REPO_URL is empty when triggered by pipeline

When a CodeBuild is triggered by a CodePipeline, the variable CODEBUILD_SOURCE_REPO_URL is empty. This is as designed, according to the documentation:

CODEBUILD_SOURCE_REPO_URL
The URL to the input artifact or source code repository. For Amazon S3, this is s3:// followed by the bucket name and path to the input artifact. For CodeCommit and GitHub, this is the repository's clone URL. If a build originates from CodePipeline, then this might be empty.

However, the script assumes this variable to be set here.
I've tried to set this environment variable from the CodePipeline, but it's not allowed to add environment variables that start with CODEBUILD.
Also tried using codecov-node which has the same issue.

The only solution I see is to set this environment variable in our buildspec.yaml , but I was hoping there is a different solution?

[thomasrockhu]

@rolandoldengarm, what happens if you set the slug using the -r argument described here?