reproduce (this is a W=1 build):
        git remote add driver-core https://git.kernel.org/pub/scm/linux/kernel/git/driver-core/driver-core.git
        git fetch driver-core driver-core-testing
        git checkout driver-core/driver-core-testing
        b4 shazam https://lore.kernel.org/r/20260123010024.3301276-1-atomlin@atomlin.com

        git clone https://github.com/intel/lkp-tests.git ~/lkp-tests
        # apt-get install llvm-dev

        # save the config file
        COMPILER_INSTALL_PATH=$HOME/0day COMPILER=gcc-15.1.0 ~/lkp-tests/kbuild/make.cross W=1 ARCH=powerpc olddefconfig
        COMPILER_INSTALL_PATH=$HOME/0day COMPILER=gcc-15.1.0 ~/lkp-tests/kbuild/make.cross W=1 ARCH=powerpc 
        COMPILER_INSTALL_PATH=$HOME/0day COMPILER=gcc-15.1.0 ~/lkp-tests/kbuild/make.cross W=1 headers
        COMPILER_INSTALL_PATH=$HOME/0day COMPILER=gcc-15.1.0 ~/lkp-tests/kbuild/make.cross W=1 -C tools/testing/selftests