message: [docker] Use debian-slim image in client
  Use the smaller `-slim` image for the final client image.
  Test Plan: Built and ran it
  Closes:
  Approved by: rustielin
diff: @@ -21,7 +21,7 @@ RUN cargo build --release -p libra-node -p cli -p config-builder -p safety-rules
  RUN strip target/release/cli
  ### Production Image ###
  -FROM debian:buster AS prod
  +FROM debian:buster-slim AS prod
  RUN mkdir -p /opt/libra/bin /opt/libra/etc
  COPY --from=builder /libra/target/release/cli /opt/libra/bin/libra_client
  