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
        git checkout 2a9b3eb1b0838cc99aafdc50e37138538d4593bb
        # 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