reproduce (this is a W=1 build):
        # https://git.kernel.org/pub/scm/linux/kernel/git/lee/mfd.git/commit/?id=9d2182e9a7b9e26cd6ee9b4831bc8538e5b0b10f
        git remote add lee-mfd https://git.kernel.org/pub/scm/linux/kernel/git/lee/mfd.git
        git fetch --no-tags lee-mfd for-mfd-next
        git checkout 9d2182e9a7b9e26cd6ee9b4831bc8538e5b0b10f
        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=$HOME/0day COMPILER=gcc-15.1.0 ~/lkp-tests/kbuild/make.cross W=1 O=build_dir ARCH=powerpc olddefconfig
        COMPILER_INSTALL_PATH=$HOME/0day COMPILER=gcc-15.1.0 ~/lkp-tests/kbuild/make.cross W=1 O=build_dir ARCH=powerpc SHELL=/bin/bash