[Kernel CI] Use Fuchsia Clang

[Andarwinux]

This is a fully tested nightly LLVM toolchain built by Google LUCI, "live at HEAD"

Introduction: ClangBuiltLinux/llvm-distributors-conf-2021#14
CI Status: https://luci-milo.appspot.com/ui/p/fuchsia/builders/luci.fuchsia.prod/clang-linux-x64
Repo: https://chrome-infra-packages.appspot.com/p/fuchsia/third_party/clang/linux-amd64

[Locietta]

Thanks for bringing this up! I wonder if there's an easy way to find the commit on which the Fuchsia clang is built. Currently, clang -dumpversion shows 20.0.0git. Is it possible to generate the version in a format like 20.0.0@7475156d4?

[Andarwinux]

Thanks for bringing this up! I wonder if there's an easy way to find the commit on which the Fuchsia clang is built. Currently, clang -dumpversion shows 20.0.0git. Is it possible to generate the version in a format like 20.0.0@7475156d4?

I think __VERSION__ might be better, like Fuchsia clang version 20.0.0git (https://llvm.googlesource.com/llvm-project) 7475156d49406785a974b1205d11fe3de9c1553e)