reproduce (this is a W=1 build):
        git clone https://github.com/intel/lkp-tests.git ~/lkp-tests
        # https://github.com/l1k/linux/commit/d8df4fbe15804f6b84dce2f91b07679f2c89fe12
        git remote add l1k https://github.com/l1k/linux
        git fetch --no-tags l1k doe
        git checkout d8df4fbe15804f6b84dce2f91b07679f2c89fe12
        # save the config file
        mkdir build_dir && cp config build_dir/.config
        ~/lkp-tests/kbuild/make.cross W=1 O=build_dir ARCH=powerpc olddefconfig
        ~/lkp-tests/kbuild/make.cross W=1 O=build_dir ARCH=powerpc SHELL=/bin/bash fs/btrfs/ lib/spdm/