misc jenkins fixups (#24840)

* bump cereal

* remove that

* pull cl image

* lil docker cleanup

tools/sim/Dockerfile.sim

@@ -1,9 +1,9 @@
 FROM ghcr.io/commaai/openpilot-base-cl:latest
 
-RUN apt-get update && apt-get install -y --no-install-recommends\
-    tmux \
-    vim \
-  && rm -rf /var/lib/apt/lists/*
+RUN apt-get update && apt-get install -y --no-install-recommends \
+      tmux \
+      vim \
+    && rm -rf /var/lib/apt/lists/*
 
 # get same tmux config used on NEOS for debugging
 RUN cd $HOME && \
@@ -27,6 +27,6 @@ COPY ./system $HOME/openpilot/system
 COPY ./tools $HOME/openpilot/tools
 
 WORKDIR $HOME/openpilot
-RUN scons -j12
+RUN scons --cache-readonly -j12
 
 RUN python -c "from selfdrive.test.helpers import set_params_enabled; set_params_enabled()"