reproduce (this is a W=1 build):
        git remote add brauner-vfs https://git.kernel.org/pub/scm/linux/kernel/git/vfs/vfs.git
        git fetch brauner-vfs vfs.all
        git checkout brauner-vfs/vfs.all
        b4 shazam https://lore.kernel.org/r/5b7bf494b1ec816111ab34416dcde85c0bc01a0a.1766848778.git.bcodding@hammerspace.com

        # save the config file
        mkdir build_dir && cp config build_dir/.config
        make W=1 O=build_dir ARCH=um olddefconfig
        make W=1 O=build_dir ARCH=um SHELL=/bin/bash