reproduce (this is a W=1 build):
        # https://git.kernel.org/pub/scm/linux/kernel/git/mingo/tip.git/commit/?id=ff1735ccc470808033db2520554f2ca090a12393
        git remote add mingo-tip https://git.kernel.org/pub/scm/linux/kernel/git/mingo/tip.git
        git fetch --no-tags mingo-tip WIP.x86/cpu
        git checkout ff1735ccc470808033db2520554f2ca090a12393

        # 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 mm/