Brandon MitchellI'm not a #bazel user, but my own project is used by their rules_oci builder. Essentially they took a bunch of existing community projects and wrapped them with some scripting. Except those projects aren't designed to build OCI images, it's more of a hack. So I've got hope that rules_img will gain traction since they used OCI libraries to make their own builder commands.
That said, if you only want to add a layer to an image, tools like crane and regctl support that today. Tools that build images tend to have a lot more functionality.
https://github.com/google/go-containerregistry/blob/main/cmd/crane/doc/crane_append.md