reproduce (this is a W=1 build):
        # https://git.kernel.org/pub/scm/linux/kernel/git/superm1/linux.git/commit/?id=74b0183524154e17897a7789da06a937eaf8b2b7
        git remote add amd-pstate https://git.kernel.org/pub/scm/linux/kernel/git/superm1/linux.git
        git fetch --no-tags amd-pstate superm1/lockdown-iommu
        git checkout 74b0183524154e17897a7789da06a937eaf8b2b7

        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=$HOME/0day COMPILER=gcc-8.5.0 ~/lkp-tests/kbuild/make.cross W=1 O=build_dir ARCH=arm olddefconfig
        COMPILER_INSTALL_PATH=$HOME/0day COMPILER=gcc-8.5.0 ~/lkp-tests/kbuild/make.cross W=1 O=build_dir ARCH=arm SHELL=/bin/bash drivers/tty/serial/8250/ security/lockdown/