use onbuild-based image

Dockerfile

@@ -1,8 +1 @@
 FROM atdr.meo.ws/archiveteam/grab-base:gnutls
-RUN echo deb http://deb.debian.org/debian buster-backports main contrib > /etc/apt/sources.list.d/backports.list \
- && DEBIAN_FRONTEND=noninteractive DEBIAN_PRIORITY=critical apt-get -qqy --no-install-recommends -o Dpkg::Options::=--force-confdef -o Dpkg::Options::=--force-confold -o Dpkg::Options::=--force-unsafe-io update \
- && DEBIAN_FRONTEND=noninteractive DEBIAN_PRIORITY=critical apt-get -qqy --no-install-recommends -o Dpkg::Options::=--force-confdef -o Dpkg::Options::=--force-confold -o Dpkg::Options::=--force-unsafe-io install lua-socket \
- && DEBIAN_FRONTEND=noninteractive DEBIAN_PRIORITY=critical apt-get -qqy --no-install-recommends -o Dpkg::Options::=--force-confdef -o Dpkg::Options::=--force-confold -o Dpkg::Options::=--force-unsafe-io -t buster-backports install zstd libzstd-dev libzstd1 \
- && pip install zstandard
-COPY . /grab
-RUN ln -fs /usr/local/bin/wget-lua /grab/wget-at