Cloud Build lets you build software quickly across all languages. Get complete control over defining custom workflows for building, testing, and deploying across multiple environments such as VMs, serverless, Kubernetes, or Firebase.
It is competitive, but I don't see it getting a significant amount of usage. It's been around for awhile and we never really saw it competitively. This rebranding/marketing push may move the needle on awareness, but they take a pretty rigid approach to how you define your builds which will turn people off I think. It's hard to use for common tasks.
Full details, as well as links to the demo and sample code are on the GitLab blog.