reproduce (this is a W=1 build):
        # https://git.kernel.org/pub/scm/linux/kernel/git/gregkh/usb.git/commit/?id=0f0ea552cd215a01baca1e99eec02e2f8df0c897
        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 0f0ea552cd215a01baca1e99eec02e2f8df0c897

        git clone https://github.com/intel/lkp-tests.git ~/lkp-tests

        # save the config file
        mkdir build_dir && cp config build_dir/.config
        COMPILER_INSTALL_PATH=$HOME/0day COMPILER=gcc-8.5.0 ~/lkp-tests/kbuild/make.cross W=1 O=build_dir ARCH=s390 olddefconfig
        COMPILER_INSTALL_PATH=$HOME/0day COMPILER=gcc-8.5.0 ~/lkp-tests/kbuild/make.cross W=1 O=build_dir ARCH=s390 SHELL=/bin/bash drivers/usb/gadget/function/