Does something prevent distributing the patches?

Maybe I'm not understanding what people mean by "GCC plugin", but as I understand it any GCC plugin has to be released under a GPL-compatible license... that was the entire reason why plugins took so long to be available in GCC.

So I don't see how using a GCC plugin allows escape from the GPL. You've only switched copyright holders from the Linux kernel community to the Free Software Foundation (sole copyright holders on GCC).

Now, if/when the kernel is able to be compiled with LLVM/Clang then certain completely proprietary plugins for that compiler can be made available under essentially any license.