reproduce (this is a W=1 build):
        git remote add cifs git://git.samba.org/sfrench/cifs-2.6.git
        git fetch --no-tags cifs for-next-next
        git checkout 4fb53948f97f5e89700fa933ba7d928ba1980f06

        # 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/smb/client/