reproduce:
        git clone https://github.com/intel/lkp-tests.git ~/lkp-tests
        # apt-get install sparse
        # sparse version: v0.6.4-66-g0196afe1
        # https://github.com/koverstreet/bcachefs/commit/010c89468134d1991b87122379f86feae23d512f
        git remote add koverstreet-bcachefs https://github.com/koverstreet/bcachefs
        git fetch --no-tags koverstreet-bcachefs master
        git checkout 010c89468134d1991b87122379f86feae23d512f
        # save the config file
        mkdir build_dir && cp config build_dir/.config
        COMPILER_INSTALL_PATH=$HOME/0day COMPILER=gcc-10.3.0 ~/lkp-tests/kbuild/make.cross C=1 CF='-fdiagnostic-prefix -D__CHECK_ENDIAN__ -fmax-errors=unlimited -fmax-warnings=unlimited' O=build_dir ARCH=sparc olddefconfig
        COMPILER_INSTALL_PATH=$HOME/0day COMPILER=gcc-10.3.0 ~/lkp-tests/kbuild/make.cross C=1 CF='-fdiagnostic-prefix -D__CHECK_ENDIAN__ -fmax-errors=unlimited -fmax-warnings=unlimited' O=build_dir ARCH=sparc SHELL=/bin/bash fs/bcachefs/