reproduce (this is a W=1 build):
        git clone https://github.com/intel/lkp-tests.git ~/lkp-tests
        # https://git.kernel.org/pub/scm/linux/kernel/git/matttbe/net-next.git/commit/?id=12cb71cbc372b584cd0f99a8b3d968a98f89aec1
        git remote add matttbe-net-next https://git.kernel.org/pub/scm/linux/kernel/git/matttbe/net-next.git
        git fetch --no-tags matttbe-net-next master
        git checkout 12cb71cbc372b584cd0f99a8b3d968a98f89aec1
        # save the config file
        mkdir build_dir && cp config build_dir/.config
        COMPILER_INSTALL_PATH=$HOME/0day COMPILER=gcc-11.5.0 ~/lkp-tests/kbuild/make.cross W=1 O=build_dir ARCH=mips olddefconfig
        COMPILER_INSTALL_PATH=$HOME/0day COMPILER=gcc-11.5.0 ~/lkp-tests/kbuild/make.cross W=1 O=build_dir ARCH=mips SHELL=/bin/bash net/mptcp/