Dockerfile.ubi: enable sccache caching

[dtrifiro]

• cherry pick from upstream: [CI/Build] Fix machete generated kernel files ordering (8976)
• Dockerfile.ubi: silence docker build warnings
• Dockerfile.ubi: adjust max_jobs/nvcc_threads
• Dockerfile.ubi: use sccache
• Dockerfile.ubi: switch from build args to --mount=type=secret

Usage example:

export AWS_ACCESS_KEY_ID=<key>
export AWS_SECRET_ACCESS_KEY=<key>

docker build --tag vllm:sccache-test -f Dockerfile.ubi --progress=plain --build-arg=max_jobs=12 --build-arg=nvcc_threads=2 --secret id=AWS_ACCESS_KEY_ID --secret id=AWS_SECRET_ACCESS_KEY

[openshift-ci]

Skipping CI for Draft Pull Request.
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You can still manually trigger a test run with /test all

[openshift-ci]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: dtrifiro

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