Is it possible to set up mirroring when importing repositories with a manifest?

Is it possible to set up mirroring when importing repositories with a manifest? I don’t want to go an enable mirroring manually for the imported projects. I would much rather generate the manifest so that it enables mirroring for each imported submodule automatically during the import.

I want to mirror boost to our local GitLab server in order backport certain compiler compatibility fixes to the latest released version. Setting up mirroring for boost manually will be really annoying. Each feature/subproject in boost is a separate submodule and I will have to setup mirroring for each of them