Merge patch series "CI: use mirrors for GNU tools"

Quentin Schulz <foss+uboot@0leil.net> says:

I have to add one (1) package to the Dockerfile as a new dependency and
wanted to build the image to verify it works. I wasn't able to because
GNU servers are just not reliable at all.

The git server URL we're using doesn't seem to be a mirrored one, and
switching to mirror URLs seem to make fetching possible again.

Unfortunately, we don't have the option to do that for coreboot's
dependencies, though we can ask coreboot to download the dependencies
through its own mirror, which we do in this series.

Link: https://lore.kernel.org/r/20251127-gnu-mirror-v2-0-c86fa2e8d464@cherry.de

diff --cc tools/docker/Dockerfile
Simple merge