reproduce (this is a W=1 build):
        git checkout next-20260202
        b4 shazam https://lore.kernel.org/r/20260203103000.20206-12-david.laight.linux@gmail.com
        # apt-get install llvm-dev

        # save the config file
        make W=1 ARCH=x86_64 olddefconfig
        make W=1 ARCH=x86_64 
        make W=1 headers_install
        make W=1 -C tools/testing/selftests