reproduce (this is a W=1 build):
        # https://git.kernel.org/pub/scm/linux/kernel/git/vbabka/linux.git/commit/?id=9cf588249e9d08717e9d9c78815474e8ea767849
        git remote add vbabka https://git.kernel.org/pub/scm/linux/kernel/git/vbabka/linux.git
        git fetch --no-tags vbabka slub-percpu-sheaves-v5-benchmarking
        git checkout 9cf588249e9d08717e9d9c78815474e8ea767849
        # 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