[Bug] epoll for container discovery is only packaged for amd64 images

[andrewazores]

Current Behavior

#371 (comment)

Expected Behavior

No response

Steps To Reproduce

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Environment

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Anything else?

No response

[andrewazores]

#373 (comment)

[andrewazores]

Another idea: do an action matrix across the build architectures, then export the image to a tarball and upload that to an artifact named like cryostat-${ref}-${arch}.

https://github.com/actions/upload-artifact/blob/main/docs/MIGRATION.md#multiple-uploads-to-the-same-named-artifact

Then a new job should follow which depends on the completion of the previous matrix job, and downloads all artifacts that match the cryostat-ref-* pattern. This job will import the image tarballs, create a manifest, add the images to the manifest, and push the manifest to registry.

https://github.com/orgs/community/discussions/42010

This way the builds can be done in parallel on different runners, and the build architecture can be passed directly to mvn -Dbuild.arch instead of using the Dockerfile.builder and the implicit $TARGETARCH, which doesn't seem to be working as intended in the workflow.