reproduce (this is a W=1 build):
        # https://git.kernel.org/pub/scm/linux/kernel/git/tj/sched_ext.git/commit/?id=7443f4ccb9e360cd50e991db81d27e3514f1be65
        git remote add tj-sched-ext https://git.kernel.org/pub/scm/linux/kernel/git/tj/sched_ext.git
        git fetch --no-tags tj-sched-ext scx-hier-prototype
        git checkout 7443f4ccb9e360cd50e991db81d27e3514f1be65
        # save the config file
        mkdir build_dir && cp config build_dir/.config
        make W=1 O=build_dir ARCH=x86_64 olddefconfig
        make W=1 O=build_dir ARCH=x86_64 SHELL=/bin/bash kernel/