Issues when building a Devbox Project with `--engine=podman`

The Dockerfile that we are generating appears to be incompatible with Podman, because we are using features that are only supported by Docker. Some issues we've encountered:

• Our COPY steps use the --link flag, which is not supported by Podman:

  [1/3] STEP 4/5: COPY --link ./.devbox/gen/runtime.nix ./.devbox/gen/
  Error: error building at STEP "COPY --link ./.devbox/gen/runtime.nix ./.devbox/gen/": COPY only supports the --chmod=<permissions> --chown=<uid:gid> and the --from=<image|stage> flags
  

• The step SHELL [ "/busybox/sh", "-eu", "-o", "pipefail", "-c"] is ignored, because SHELL is not suported in the OCI image format.

• (Maybe related to the prior step?) The step RUN cp -rs /busybox/. /bin/ && cp -rs /busybox/. /usr/bin/ fails with the following error:

error running container: error from /usr/bin/crun creating container for [/bin/sh -c cp -rs /busybox/. /bin/ && cp -rs /busybox/. /usr/bin/]: executable file `/bin/sh` not found in $PATH: No such file or directory

These issues do not happen when running with --engine=docker, so we need to either generate a fully OCI compliant Containerfile for all engines, or have a separate Dockerfile that we use for non-Docker engines.