reproduce (this is a W=1 build):
        git remote add mptcp https://github.com/multipath-tcp/mptcp_net-next.git
        git fetch mptcp export-net
        git checkout mptcp/export-net
        b4 shazam https://lore.kernel.org/r/d3f96328a76e6fffcb871e8542c526ea99135ea5.1758039775.git.pabeni@redhat.com
        git clone https://github.com/intel/lkp-tests.git ~/lkp-tests
        # save the config file
        mkdir build_dir && cp config build_dir/.config
        COMPILER_INSTALL_PATH=$HOME/0day COMPILER=gcc-15.1.0 ~/lkp-tests/kbuild/make.cross W=1 O=build_dir ARCH=arc olddefconfig
        COMPILER_INSTALL_PATH=$HOME/0day COMPILER=gcc-15.1.0 ~/lkp-tests/kbuild/make.cross W=1 O=build_dir ARCH=arc SHELL=/bin/bash net/mptcp/