CI: use scons cache mount for building simulator and docs (#29436)

* build docker image with scons cache

* use setup

* scons cache

* added the dockerfile

* add the shell

* docs use cache

* dont pull lfs for docs

* simulator too

* dont pull the cache image

* fix inputs

* inputs

* booleans aren't supported

* bool not supported

* bool isnt supported

* fix

* readonly cache

* fix sim cache too

* respect readonly

* gitignore and move to correct folder

* also copy old

* move to tools/ci

* move to selfdrive/test

* just make the cache writable, it's discarded anyway

* minimize diff in this pr
old-commit-hash: 197460e061

tools/sim/Dockerfile.sim

@@ -1,3 +1,5 @@
+FROM scons-cache as scons-cache
+
 FROM ghcr.io/commaai/openpilot-base-cl:latest
 
 RUN apt-get update && apt-get install -y --no-install-recommends \
@@ -29,6 +31,6 @@ COPY ./system $HOME/openpilot/system
 COPY ./tools $HOME/openpilot/tools
 
 WORKDIR $HOME/openpilot
-RUN scons --cache-readonly -j12
+RUN --mount=type=bind,from=scons-cache,source=/tmp/scons_cache,target=/tmp/scons_cache,rw scons -j12
 
 RUN python -c "from openpilot.selfdrive.test.helpers import set_params_enabled; set_params_enabled()"