I don't recall seeing much recent activity on the mailing lists along these lines.

I have a very vague recollection that Linux may be dependent on gcc specific features that clang doesn't intend to support?

EDIT: "One of the major compilation problems with LLVM/CLang is that they do not support VLA’s ... widely used inside the linux kernel." from [1]

There was some activity over the prior six months or so to get lld to link the kernel (can't recall if it was built by gcc or clang for those tests).

[1] https://www.quora.com/What-is-the-state-of-the-art-of-compil...