reproduce (this is a W=1 build):
        # https://git.kernel.org/pub/scm/linux/kernel/git/cel/linux.git/commit/?id=a5860f87bf2b5c77071640da909e49584284ec73
        git remote add cel https://git.kernel.org/pub/scm/linux/kernel/git/cel/linux
        git fetch --no-tags cel nfsd-6.1.y
        git checkout a5860f87bf2b5c77071640da909e49584284ec73
        # save the config file
        mkdir build_dir && cp config build_dir/.config
        make W=1 O=build_dir ARCH=i386 olddefconfig
        make W=1 O=build_dir ARCH=i386 SHELL=/bin/bash fs/nfsd/