reproduce (this is a W=1 build):
        git clone https://github.com/intel/lkp-tests.git ~/lkp-tests
        # install powerpc cross compiling tool for clang build
        # apt-get install binutils-powerpc-linux-gnu
        # clang-21 might not be officially released. Try a lower version if installation fails.
        # https://github.com/chleroy/linux/commit/ddfbac9ee97c521bcc7bc856f90384363f7e2f74
        git remote add chleroy https://github.com/chleroy/linux
        git fetch --no-tags chleroy uaccess_masked
        git checkout ddfbac9ee97c521bcc7bc856f90384363f7e2f74
        # save the config file
        mkdir build_dir && cp config build_dir/.config
        COMPILER_INSTALL_PATH=$HOME/0day COMPILER=clang-21 ~/lkp-tests/kbuild/make.cross W=1 O=build_dir ARCH=powerpc olddefconfig
        COMPILER_INSTALL_PATH=$HOME/0day COMPILER=clang-21 ~/lkp-tests/kbuild/make.cross W=1 O=build_dir ARCH=powerpc SHELL=/bin/bash kernel/futex/