feat: generalize container tool usage in Makefile template

[rhuss]

Description of the change:
This PR generalizes the container tool usage in the bundle build target to respect the CONTAINER_TOOL variable. The change replaces the hardcoded docker command with $(CONTAINER_TOOL) in the bundle-build target of the Makefile template, making it consistent with other container-related targets in the operator-sdk.

Motivation for the change:
Currently, the bundle build target hardcodes the use of docker as the container tool, which is inconsistent with other parts of the operator-sdk that respect the CONTAINER_TOOL variable. This change:

1. Makes the bundle build process more flexible by allowing users to use alternative container tools like podman
2. Maintains consistency with the rest of the operator-sdk tooling
3. Follows the existing pattern used in other container-related targets

Checklist

If the pull request includes user-facing changes, extra documentation is required:

• Add a new changelog fragment in changelog/fragments (see changelog/fragments/00-template.yaml)
• Add or update relevant sections of the docs website in website/content/en/docs

[camilamacedo86]

Hi @rhuss

Thank you for your contribution 🥇

I think that is OK because matches with the scaffold of kubebuilder: https://github.com/kubernetes-sigs/kubebuilder/blob/master/testdata/project-v4/Makefile

However, you need to run make install and make generate locally to ensure that those files are properly updated in the testdata.

[rhuss]

Thanks! Regenerated makefiles now.

[rhuss]

For non-go Makefiles the $CONTAINER_TOOL needs to be included in the fragment, vor go Makefiles it comes from kubebuilder. Adapted the template accordingly.

[camilamacedo86]

Hi @rhuss

Can you please rebase it with master?
Also, see that it still falling in the sanity checks. You can run make test-sanity

[rhuss]

rebased ...

[rhuss]

@camilamacedo86 I've fixed the sanity check, but the doc check fails for some reason, but I'm pretty sure this is not because of this PR.

[camilamacedo86]

I believe we shouldn't add this code here directly.
The more appropriate approach would be to update the Makefile scaffold used by Helm. You can refer to the implementation here for context:
👉 https://github.com/operator-framework/operator-sdk/blob/master/internal/plugins/helm/v1/scaffolds/internal/templates/makefile.go

Additionally, it would be great if we could add the same logic in the default Golang plugin as well, ideally on the same line. This would help us keep things consistent and easier to maintain across plugins. Could you please take a look?

Lastly, if this change is really needed here, we'd need to ensure it's applied and validated across all relevant places to keep things aligned.

Appreciate your effort—thank you! 😊