Set colcon defaults for user overlay image (#224)

Dockerfile

@@ -61,6 +61,19 @@ RUN --mount=type=cache,target=/var/cache/apt,sharing=locked \
       --from-paths src \
       --ignore-src
 
+# Set up colcon defaults for the new user
+USER ${USERNAME}
+RUN colcon mixin add default \
+    https://raw.githubusercontent.com/colcon/colcon-mixin-repository/master/index.yaml && \
+    colcon mixin update && \
+    colcon metadata add default \
+    https://raw.githubusercontent.com/colcon/colcon-metadata-repository/master/index.yaml && \
+    colcon metadata update
+COPY colcon-defaults.yaml /home/${USERNAME}/.colcon/defaults.yaml
+
+# hadolint ignore=DL3002
+USER root
+
 ###################################################################
 # Target for the developer build which does not compile any code. #
 ###################################################################

colcon-defaults.yaml

@@ -0,0 +1,17 @@
+# Contains colcon default settings for user overlay containers.
+build:
+  # Enable this for bidirectional syncing from the UI
+  symlink-install: true
+  mixin:
+    # Enable ccache support
+    - ccache
+    # Multithreaded linker to speed up linking step during compilation
+    - lld
+    - compile-commands
+    # Debug info and build testing for dev workflows
+    - rel-with-deb-info
+    - build-testing-on
+test:
+  event-handlers:
+    - console_direct+
+    - desktop_notification+