reproduce (this is a W=1 build):
        git remote add tip https://git.kernel.org/pub/scm/linux/kernel/git/tip/tip.git
        git fetch tip x86/asm
        git checkout tip/x86/asm
        b4 shazam https://lore.kernel.org/r/20230913152238.905247-3-mszeredi@redhat.com
        # save the config file
        mkdir build_dir && cp config build_dir/.config
        make W=1 O=build_dir ARCH=um SUBARCH=i386 olddefconfig
        make W=1 O=build_dir ARCH=um SUBARCH=i386 SHELL=/bin/bash