TCC did several years ago. It could boot Linux from source in under 10 seconds. It's wasn't that big of a C compiler. It's in the 50,000 lines of code range.
This was 20 years ago from what I can find. Beside that Linux now is a vastly different codebase than it was 20 years ago. That effort also did not compile Linux unmodified, it required several changes: https://bellard.org/tcc/tccboot_readme.html.