reproduce (this is a W=1 build):
        # https://github.com/zen-kernel/zen-kernel/commit/f90f6c0ad3cb7786aa8308e4669ea037dabf7476
        git remote add zen https://github.com/zen-kernel/zen-kernel
        git fetch --no-tags zen 6.9/prjc
        git checkout f90f6c0ad3cb7786aa8308e4669ea037dabf7476
        # save the config file
        mkdir build_dir && cp config build_dir/.config
        make W=1 O=build_dir ARCH=i386 olddefconfig
        make W=1 O=build_dir ARCH=i386 SHELL=/bin/bash kernel/sched/