reproduce (this is a W=1 build):
        git clone https://github.com/intel/lkp-tests.git ~/lkp-tests
        # install arm64 cross compiling tool for clang build
        # apt-get install binutils-aarch64-linux-gnu
        # clang-21 might not be officially released. Try a lower version if installation fails.
        # https://github.com/norov/linux/commit/f66f9c3d09c12f6ceea17d1ba22be2cb8bc9e4e4
        git remote add norov https://github.com/norov/linux
        git fetch --no-tags norov bitmap-for-next
        git checkout f66f9c3d09c12f6ceea17d1ba22be2cb8bc9e4e4
        # save the config file
        mkdir build_dir && cp config build_dir/.config
        COMPILER_INSTALL_PATH=$HOME/0day COMPILER=clang-21 ~/lkp-tests/kbuild/make.cross W=1 O=build_dir ARCH=arm64 olddefconfig
        COMPILER_INSTALL_PATH=$HOME/0day COMPILER=clang-21 ~/lkp-tests/kbuild/make.cross W=1 O=build_dir ARCH=arm64 SHELL=/bin/bash arch/arm64/kvm/