[WIP] feat: add cdi-spec-dir option to top level options

[micahcc]

In response to #18292.

One of the primary benefits of podman is that its possible run without altering the host system. By allowing cdi directories to be passed via command line it maintains this feature.

I'm particularly interested in running podman in a nix-shell with nvidia GPU passthough. Podman and all its dependencies (including nvidia-container-toolkit) come from nix and the host system again doesn't need altering. The one problem with that right now is that I have to write /etc/cdi/nvidia.yaml to be able to use the GPU. Note that the old nvidia-runtime-hook does not work for my use case (which involves vulkan passthrough).

With this change it will be possible to generate a user nvidia.yaml and point podman at that user-specific mount instructions there.

Does this PR introduce a user-facing change?

- Add cdi-spec-dir option to insert additional CDI Spec search paths into the CDI loader.

[openshift-ci]

[APPROVALNOTIFIER] This PR is NOT APPROVED

This pull-request has been approved by: micahcc
Once this PR has been reviewed and has the lgtm label, please assign flouthoc for approval. For more information see the Kubernetes Code Review Process.

The full list of commands accepted by this bot can be found here.

Needs approval from an approver in each of these files:

• OWNERS

Approvers can indicate their approval by writing /approve in a comment
Approvers can cancel approval by writing /approve cancel in a comment

[micahcc]

Needs: containers/common#1834

[github-actions]

A friendly reminder that this PR had no activity for 30 days.

[packit-as-a-service]

Ephemeral COPR build failed. @containers/packit-build please check.

[abergeron]

Is there any intention of merging this PR?

I did try to use the cdi_spec_dirs option for a project only to spend days wondering what I did wrong as it didn't work and eventually ending up here to realize that it doesn't work because it was never hooked up in the code to do something.

As best as I understand, this PR is what would make it do that something.

[isbecker]

@micahcc are you able to move this forward now?
The required containers/common#1834 is merged upstream and even #25171 was merged for CDI support with podman-compose.