reproduce (this is a W=1 build):
        git clone https://github.com/intel/lkp-tests.git ~/lkp-tests
        # https://github.com/avpatel/linux/commit/8fb05f222ccd411de35ca6e6e5302268d23745bd
        git remote add avpatel https://github.com/avpatel/linux.git
        git fetch --no-tags avpatel riscv_raid6_rvv_v5
        git checkout 8fb05f222ccd411de35ca6e6e5302268d23745bd
        # save the config file
        mkdir build_dir && cp config build_dir/.config
        COMPILER_INSTALL_PATH=$HOME/0day COMPILER=gcc-7.5.0 ~/lkp-tests/kbuild/make.cross W=1 O=build_dir ARCH=riscv olddefconfig
        COMPILER_INSTALL_PATH=$HOME/0day COMPILER=gcc-7.5.0 ~/lkp-tests/kbuild/make.cross W=1 O=build_dir ARCH=riscv SHELL=/bin/bash