reproduce (this is a W=1 build):
        # https://github.com/zen-kernel/zen-kernel/commit/4552ae443b368caad94ec1a5dfb1e92047dc62a6
        git remote add zen https://github.com/zen-kernel/zen-kernel
        git fetch --no-tags zen 7.2/zen-sauce
        git checkout 4552ae443b368caad94ec1a5dfb1e92047dc62a6
        # apt-get install sparse
        # sparse: v0.6.5-rc1

        # save the config file
        mkdir build_dir && cp config build_dir/.config
        make W=1 C=1 CF='-fdiagnostic-prefix -D__CHECK_ENDIAN__ -fmax-errors=unlimited -fmax-warnings=unlimited' O=build_dir ARCH=um olddefconfig
        make W=1 C=1 CF='-fdiagnostic-prefix -D__CHECK_ENDIAN__ -fmax-errors=unlimited -fmax-warnings=unlimited' O=build_dir ARCH=um SHELL=/bin/bash drivers/gpu/drm/ttm/ fs/btrfs/