reproduce (this is a W=1 build):
        git clone https://github.com/intel/lkp-tests.git ~/lkp-tests
        # https://github.com/esmil/linux/commit/a9aca05338c63b95eb676983ee677d5cc4590501
        git remote add esmil https://github.com/esmil/linux
        git fetch --no-tags esmil th1520
        git checkout a9aca05338c63b95eb676983ee677d5cc4590501
        # save the config file
        mkdir build_dir && cp config build_dir/.config
        ~/lkp-tests/kbuild/make.cross W=1 O=build_dir ARCH=riscv olddefconfig
        ~/lkp-tests/kbuild/make.cross W=1 O=build_dir ARCH=riscv SHELL=/bin/bash dtbs_check