[llvm] workflows/build-ci-container: Add an arm64 container (PR #120828)

[Tom Stellard via llvm-commits]

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@@ -33,8 +38,8 @@ jobs:
       - name: Write Variables
         id: vars
         run: |
-          tag=`date +%s`
-          container_name="ghcr.io/$GITHUB_REPOSITORY_OWNER/ci-ubuntu-22.04"
+          tag="${{ github.run_id}}.${{ github.run_attempt }}"
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tstellar wrote:

We could use the short commit SHA.

I'm not sure about the arch suffix.  For Fedora containers we have the arch suffix:
`registry.fedoraproject.org/fedora:41-aarch64`

But for ubuntu there is no suffix and the arch is in the namespace: `docker.io/arm64v8/ubuntu:22.04`

I really  have no preference, I just want to be consistent with whatever the convention is.

https://github.com/llvm/llvm-project/pull/120828