reproduce (this is a W=1 build):
        # https://git.kernel.org/pub/scm/linux/kernel/git/gregkh/driver-core.git/commit/?id=2aa9af21ca6842da988fabdacbb2fa8278182c7a
        git remote add driver-core https://git.kernel.org/pub/scm/linux/kernel/git/gregkh/driver-core.git
        git fetch --no-tags driver-core simple_bus
        git checkout 2aa9af21ca6842da988fabdacbb2fa8278182c7a
        # save the config file
        mkdir build_dir && cp config build_dir/.config
        make W=1 O=build_dir ARCH=i386 olddefconfig
        make W=1 O=build_dir ARCH=i386 SHELL=/bin/bash drivers/base/