Added suport for building multi-arch images

[AverageMarcus]

Changes

Partial work towards #856
Adds support for building images for other architectures.

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• Includes tests (if functionality changed/added)
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Reviewer Notes

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Release Notes

[tekton-robot]

Hi @AverageMarcus. Thanks for your PR.

I'm waiting for a tektoncd member to verify that this patch is reasonable to test. If it is, they should reply with /ok-to-test on its own line. Until that is done, I will not automatically test new commits in this PR, but the usual testing commands by org members will still work. Regular contributors should join the org to skip this step.

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[vdemeester]

/kind misc
/ok-to-test

[afrittoli]

Thanks, this looks good!
Approving and lgtm since #3314 was already approved.

/approve
/lgtm

[tekton-robot]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: afrittoli, vdemeester

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[imjasonh]

/lgtm

Thanks!

[imjasonh]

/test pull-tekton-pipeline-integration-tests