reproduce (this is a W=1 build):
        # https://git.kernel.org/pub/scm/linux/kernel/git/jirislaby/linux.git/commit/?id=a79ca9cf1590b4c025eb1af2fd9892b562421525
        git remote add jirislaby https://git.kernel.org/pub/scm/linux/kernel/git/jirislaby/linux.git
        git fetch --no-tags jirislaby devel
        git checkout a79ca9cf1590b4c025eb1af2fd9892b562421525
        # save the config file
        mkdir build_dir && cp config build_dir/.config
        make W=1 O=build_dir ARCH=x86_64 olddefconfig
        make W=1 O=build_dir ARCH=x86_64 SHELL=/bin/bash drivers/tty/serial/