reproduce (this is a W=1 build):
        # https://git.kernel.org/pub/scm/linux/kernel/git/ebiggers/linux.git/commit/?id=2087a31445f0be98a499611a2d0bd798d21a76c4
        git remote add ebiggers https://git.kernel.org/pub/scm/linux/kernel/git/ebiggers/linux.git
        git fetch --no-tags ebiggers wip-rng
        git checkout 2087a31445f0be98a499611a2d0bd798d21a76c4

        # 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 crypto/