If the build process in Cloud Build requires a build tool not in the environment, what is the best course of action?

Building a custom cloud builder image is the most effective solution when the necessary build tool is not available in the Cloud Build environment. This approach allows you to define a custom Docker image that contains all the required dependencies, libraries, and tools specific to your build process. By doing this, you ensure a consistent and repeatable build environment, as the image can be reused across multiple builds without the concern of missing tools or dependencies.

Once you have created and stored this custom image in a container registry, you can easily reference it in your Cloud Build configuration. This eliminates the potential issues associated with downloading binaries during the build process, such as dependencies on external resources, network reliability, or version conflicts.

In contrast, downloading a binary from the internet during the build process can introduce risks including potential downtime of the download source or changes to the file that could affect the build. Including the binary in Cloud Source Repositories can increase repository size and complicate version management, and relying on others to add binaries to the Cloud Build environment limits your control over the build process and might not align with your project's specific needs. Building a custom cloud builder is, therefore, the most viable and robust option.