reproduce (this is a W=1 build):
        # https://git.kernel.org/pub/scm/linux/kernel/git/herbert/cryptodev-2.6.git/commit/?id=10a6d72ea355b730aa9702da0fd36aef0898a80e
        git remote add herbert-cryptodev-2.6 https://git.kernel.org/pub/scm/linux/kernel/git/herbert/cryptodev-2.6.git
        git fetch --no-tags herbert-cryptodev-2.6 master
        git checkout 10a6d72ea355b730aa9702da0fd36aef0898a80e
        # 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