If you use the Amazon Linux 2 (AL2) standard image version 1.0 or later, or the Ubuntu standard image version 2.0 or later, you can specify one or more runtimes in the runtime-versions section of your buildspec file. This sample shows how you can change your project runtime, specify more than one runtime, and specify a runtime that is dependent on another runtime.

https://docs.aws.amazon.com/codebuild/latest/userguide/sample-runtime-versions.html