CI: Add GOTOOLCHAIN=local to prevent automatic toolchain downloads#14957

Copilot wants to merge 3 commits intomaingithub/gh-aw:mainfrom

copilot/fix-9919-1036865607-2fb99207-f1ef-43a0-95f9-eafd0d86d70agithub/gh-aw:copilot/fix-9919-1036865607-2fb99207-f1ef-43a0-95f9-eafd0d86d70aCopy head branch name to clipboard