reproduce (this is a W=1 build):
        # https://git.kernel.org/pub/scm/linux/kernel/git/gregkh/usb.git/commit/?id=b3c9b6925ca2e02ef2fd77d0aa5e0ca6b2a67f5a
        git remote add usb https://git.kernel.org/pub/scm/linux/kernel/git/gregkh/usb.git
        git fetch --no-tags usb usb-testing
        git checkout b3c9b6925ca2e02ef2fd77d0aa5e0ca6b2a67f5a

        # 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