reproduce (this is a W=1 build):
        git remote add xfs git://git.kernel.org:/pub/scm/fs/xfs/xfs-linux
        git fetch --no-tags xfs xfs-7.4-merge
        git checkout 1e4c3089ab63d3afee702243630d9c3c919a046b

        # save the config file
        mkdir build_dir && cp config build_dir/.config
        make W=1 O=build_dir ARCH=x86_64 olddefconfig
        make W=1 O=build_dir ARCH=x86_64 SHELL=/bin/bash fs/xfs/