ci: Allow build dir on CI host

ci/test/02_run_container.sh

@@ -44,18 +44,21 @@ if [ -z "$DANGER_RUN_CI_ON_HOST" ]; then
   CI_DEPENDS_MOUNT="type=volume,src=${CONTAINER_NAME}_depends,dst=$DEPENDS_DIR/built"
   CI_DEPENDS_SOURCES_MOUNT="type=volume,src=${CONTAINER_NAME}_depends_sources,dst=$DEPENDS_DIR/sources"
   CI_PREVIOUS_RELEASES_MOUNT="type=volume,src=${CONTAINER_NAME}_previous_releases,dst=$PREVIOUS_RELEASES_DIR"
+  CI_BUILD_MOUNT=""
 
-  if [ "$DANGER_CI_ON_HOST_CACHE_FOLDERS" ]; then
+  if [ "$DANGER_CI_ON_HOST_FOLDERS" ]; then
     # ensure the directories exist
     mkdir -p "${CCACHE_DIR}"
     mkdir -p "${DEPENDS_DIR}/built"
     mkdir -p "${DEPENDS_DIR}/sources"
     mkdir -p "${PREVIOUS_RELEASES_DIR}"
+    mkdir -p "${BASE_BUILD_DIR}"  # Unset by default, must be defined externally
 
     CI_CCACHE_MOUNT="type=bind,src=${CCACHE_DIR},dst=$CCACHE_DIR"
     CI_DEPENDS_MOUNT="type=bind,src=${DEPENDS_DIR}/built,dst=$DEPENDS_DIR/built"
     CI_DEPENDS_SOURCES_MOUNT="type=bind,src=${DEPENDS_DIR}/sources,dst=$DEPENDS_DIR/sources"
     CI_PREVIOUS_RELEASES_MOUNT="type=bind,src=${PREVIOUS_RELEASES_DIR},dst=$PREVIOUS_RELEASES_DIR"
+    CI_BUILD_MOUNT="--mount type=bind,src=${BASE_BUILD_DIR},dst=${BASE_BUILD_DIR}"
   fi
 
   if [ "$DANGER_CI_ON_HOST_CCACHE_FOLDER" ]; then
@@ -97,6 +100,7 @@ if [ -z "$DANGER_RUN_CI_ON_HOST" ]; then
                   --mount "${CI_DEPENDS_MOUNT}" \
                   --mount "${CI_DEPENDS_SOURCES_MOUNT}" \
                   --mount "${CI_PREVIOUS_RELEASES_MOUNT}" \
+                  ${CI_BUILD_MOUNT} \
                   --env-file /tmp/env-$USER-$CONTAINER_NAME \
                   --name "$CONTAINER_NAME" \
                   --network ci-ip6net \