The feature to support customizing the docker file name introduced in #5652 will pass the full absolute path of the docker file name to docker build. This happens both for the case where a custom docker file name is specified and when it is not specified (defaults to /full/path/to/Dockerfile).

However, since we are staging the build directory into cdk.out (which can potentially be ported to a different system, e.g. as part of a CI/CD process), we need the name of the custom docker file to be relative and not absolute.

See https://github.com/aws/aws-cdk/pull/5652/files#r366863153

This is 🐛 Bug Report