reproduce (this is a W=1 build):
        # https://git.kernel.org/pub/scm/linux/kernel/git/vireshk/linux.git/commit/?id=a48f3f89a6e63a510bc77d374dc291066dcef8f6
        git remote add vireshk https://git.kernel.org/pub/scm/linux/kernel/git/vireshk/linux.git
        git fetch --no-tags vireshk virtio/msg
        git checkout a48f3f89a6e63a510bc77d374dc291066dcef8f6
        # 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/virtio/