reproduce (this is a W=1 build):
        git checkout a6fb923f7803f40a567445dfe1ff3a539c8adc1f
        # 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 net/