reproduce (this is a W=1 build):
        git clone https://github.com/intel/lkp-tests.git ~/lkp-tests
        # https://github.com/ambarus/linux-0day/commit/2fe5adeaab12de539cebb3a3d3fe321f4d267d53
        git remote add ambarus https://github.com/ambarus/linux-0day
        git fetch --no-tags ambarus mtd/spimem-odd-octal-ops
        git checkout 2fe5adeaab12de539cebb3a3d3fe321f4d267d53
        # save the config file
        mkdir build_dir && cp config build_dir/.config
        COMPILER_INSTALL_PATH=$HOME/0day COMPILER=clang-21 ~/lkp-tests/kbuild/make.cross W=1 O=build_dir ARCH=hexagon olddefconfig
        COMPILER_INSTALL_PATH=$HOME/0day COMPILER=clang-21 ~/lkp-tests/kbuild/make.cross W=1 O=build_dir ARCH=hexagon SHELL=/bin/bash drivers/mtd/spi-nor/