reproduce (this is a W=1 build):
        # https://git.kernel.org/pub/scm/linux/kernel/git/niks/linux.git/commit/?id=4ada123c36723c3ef6a6179839aa39a7901b710e
        git remote add niks https://git.kernel.org/pub/scm/linux/kernel/git/niks/linux.git
        git fetch --no-tags niks has_ioport
        git checkout 4ada123c36723c3ef6a6179839aa39a7901b710e
        # save the config file
        mkdir build_dir && cp config build_dir/.config
        make W=1 O=build_dir ARCH=um olddefconfig
        make W=1 O=build_dir ARCH=um SHELL=/bin/bash drivers/tty/serial/8250/