reproduce (this is a W=1 build):
        # https://git.kernel.org/pub/scm/linux/kernel/git/arnd/asm-generic.git/commit/?id=824c915b5b0011418f9000ee1c2b4299b842595a
        git remote add arnd-asm-generic https://git.kernel.org/pub/scm/linux/kernel/git/arnd/asm-generic.git
        git fetch --no-tags arnd-asm-generic syscall-tbl-6.11
        git checkout 824c915b5b0011418f9000ee1c2b4299b842595a
        # 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