fix apt installs in Dockerfile template

Author: gilesknap

template/Dockerfile.jinja

@@ -1,9 +1,11 @@
 # The developer stage is used as a devcontainer including dev versions
 # of the build dependencies
 FROM ghcr.io/diamondlightsource/ubuntu-devcontainer:noble AS developer
-RUN apt-get update -y && apt-get install -y --no-install-recommends \
-    libevent-dev \
-    libreadline-dev{% if docker %}
+
+# Add any system dependencies for the developer/build environment here
+RUN apt-get update && apt-get install -y --no-install-recommends \
+    graphviz \
+    && rm -rf /var/lib/apt/lists/*
 
 # The build stage makes some assets using the developer tools
 FROM developer AS build
@@ -26,10 +28,11 @@ RUN --mount=type=cache,target=/root/.cache/uv \
 # The runtime stage installs runtime deps then copies in built assets
 # This time we remove the apt lists to save disk space
 FROM ubuntu:noble as runtime
-RUN apt-get update -y && apt-get install -y --no-install-recommends \
-    libevent \
-    libreadline \
-    && rm -rf /var/lib/apt/lists/*
+
+# Add apt-get system dependecies for runtime here if needed
+{# RUN apt-get update && apt-get install -y --no-install-recommends \
+    xxx \
+    && rm -rf /var/lib/apt/lists/* #}
 COPY --from=build /assets /
 
 # We need to keep the venv at the same absolute path as in the build stage