reproduce (this is a W=1 build):
        git clone https://github.com/intel/lkp-tests.git ~/lkp-tests
        # https://github.com/zen-kernel/zen-kernel/commit/87b0cab8d8701db7754e5778b93ff83ffc64c7ae
        git remote add zen https://github.com/zen-kernel/zen-kernel
        git fetch --no-tags zen 6.12/zen-sauce
        git checkout 87b0cab8d8701db7754e5778b93ff83ffc64c7ae
        # save the config file
        mkdir build_dir && cp config build_dir/.config
        COMPILER_INSTALL_PATH=$HOME/0day COMPILER=gcc-14.2.0 ~/lkp-tests/kbuild/make.cross W=1 O=build_dir ARCH=sh olddefconfig
        COMPILER_INSTALL_PATH=$HOME/0day COMPILER=gcc-14.2.0 ~/lkp-tests/kbuild/make.cross W=1 O=build_dir ARCH=sh SHELL=/bin/bash fs/bcachefs/