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/phy/linux-phy.git/commit/?id=9c8504861cc4102463f31fe1f5e120a6deb15c15
        git remote add phy https://git.kernel.org/pub/scm/linux/kernel/git/phy/linux-phy.git
        git fetch --no-tags phy next
        git checkout 9c8504861cc4102463f31fe1f5e120a6deb15c15
        # save the config file
        mkdir build_dir && cp config build_dir/.config
        COMPILER_INSTALL_PATH=$HOME/0day COMPILER=gcc-15.1.0 ~/lkp-tests/kbuild/make.cross W=1 O=build_dir ARCH=m68k olddefconfig
        COMPILER_INSTALL_PATH=$HOME/0day COMPILER=gcc-15.1.0 ~/lkp-tests/kbuild/make.cross W=1 O=build_dir ARCH=m68k SHELL=/bin/bash