ci: disable ccache and toolkit cache for self-hosted OpenVINO runners

[Copilot]

GitHub Actions cache causes issues on self-hosted runners due to cross-OS detection — runners alternately create their own cache entries, leading to conflicts. Both the ccache and OpenVINO toolkit cache need to be fully disabled for self-hosted runners.

• build.yml: Added if: matrix.variant != 'gpu' to the ccache and Use OpenVINO Toolkit Cache steps. The gpu variant runs on self-hosted while cpu runs on ubuntu-24.04. The existing Setup OpenVINO Toolkit condition (cache-hit != 'true') naturally evaluates to true when the cache step is skipped, so the toolkit is always downloaded fresh on self-hosted.
• build-self-hosted.yml: Removed the Use OpenVINO Toolkit Cache step entirely from ggml-ci-intel-openvino-gpu-low-perf (always self-hosted) and dropped the cache-hit condition on Setup OpenVINO Toolkit so it runs unconditionally.

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[CISC]

Well, that was fruitful...

[CISC]

Ah, just a massive delay?

[ggerganov]

Yup, very slow. copilot ngmi

But I wonder if the suggestion to remove the toolkit cache from the self-hosted workflows makes sense.

[CISC]

But I wonder if the suggestion to remove the toolkit cache from the self-hosted workflows makes sense.

Yep, will do once CI finishes.

[ggerganov]

Even though the workflow is self-hosted, it seems the cache still works:

https://github.com/ggml-org/llama.cpp/actions/runs/23111057155/job/67128454815

So maybe we want to keep the toolkit cache active.

Not 100% sure.

[CISC]

Even though the workflow is self-hosted, it seems the cache still works:

It works if it was created by that os previously, otherwise it will create a new one, might as well disable it.

[ggerganov]

Yes, lets disable. It's better to put a bit more load on that runner compared to taking a bit from the GH cache.

[CISC]

Even though the workflow is self-hosted, it seems the cache still works:

It works if it was created by that os previously, otherwise it will create a new one, might as well disable it.

The cache is named with runner.os, but that's not sufficient as actions/cache has further checks it seems.