reproduce (this is a W=1 build):
        git remote add btrfs https://github.com/btrfs/linux.git
        git fetch btrfs for-next
        git checkout btrfs/for-next
        b4 shazam https://lore.kernel.org/r/48b407f8488edc890710cdf8ebfefe413e7721c2.1792391732.git.wqu@suse.com

        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=$HOME/0day COMPILER=gcc-16.2.0 ~/lkp-tests/kbuild/make.cross W=1 O=build_dir ARCH=m68k olddefconfig
        COMPILER_INSTALL_PATH=$HOME/0day COMPILER=gcc-16.2.0 ~/lkp-tests/kbuild/make.cross W=1 O=build_dir ARCH=m68k SHELL=/bin/bash fs/btrfs/