reproduce (this is a W=1 build):
        git clone https://github.com/intel/lkp-tests.git ~/lkp-tests
        # install riscv cross compiling tool for clang build
        # apt-get install binutils-riscv64-linux-gnu
        # https://git.kernel.org/pub/scm/linux/kernel/git/srini/nvmem.git/commit/?id=f5de138db5b76de7d96d4cf92f871ba893ba0119
        git remote add srini-nvmem https://git.kernel.org/pub/scm/linux/kernel/git/srini/nvmem.git
        git fetch --no-tags srini-nvmem for-next
        git checkout f5de138db5b76de7d96d4cf92f871ba893ba0119
        # save the config file
        mkdir build_dir && cp config build_dir/.config
        COMPILER_INSTALL_PATH=$HOME/0day COMPILER=clang-19 ~/lkp-tests/kbuild/make.cross W=1 O=build_dir ARCH=riscv olddefconfig
        COMPILER_INSTALL_PATH=$HOME/0day COMPILER=clang-19 ~/lkp-tests/kbuild/make.cross W=1 O=build_dir ARCH=riscv SHELL=/bin/bash drivers/mtd/ drivers/rtc/