circleci: Explicitly install cpio on DPKG systems

This is understandably no longer present on the buster base docker
image, but I'm not adding this to installation instructions in the
documentation because I hope to remove that dependency before the
next release.

.circleci/config.yml

@@ -173,6 +173,7 @@ jobs:
                     automake \
                     build-essential \
                     ca-certificates \
+                    cpio \
                     graphviz \
                     libedit-dev \
                     libjemalloc-dev \