reproduce (this is a W=1 build):
        # https://github.com/bvanassche/linux/commit/20938ba5a67fab6489f0ac9c1794318447328717
        git remote add bvanassche https://github.com/bvanassche/linux
        git fetch --no-tags bvanassche thread-safety
        git checkout 20938ba5a67fab6489f0ac9c1794318447328717
        # 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 prepare