reproduce (this is a W=1 build):
        git checkout 34b64663e85dec8dac9dd02d94a50d90000a51a7
        # 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 mm/