reproduce (this is a W=1 build):
        # https://git.kernel.org/pub/scm/linux/kernel/git/jfern/linux.git/commit/?id=21a8993e78a379a22cd049ca8b4f8ff1bae66612
        git remote add jfern https://git.kernel.org/pub/scm/linux/kernel/git/jfern/linux.git
        git fetch --no-tags jfern nova-core-experiments
        git checkout 21a8993e78a379a22cd049ca8b4f8ff1bae66612
        # 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/gpu/drm/