ci: use docker build cache arg directly

diff --git a/ci/test/02_run_container.sh b/ci/test/02_run_container.sh
index b3553f7f..eefac848 100755
--- a/ci/test/02_run_container.sh
+++ b/ci/test/02_run_container.sh
@@ -19,29 +19,6 @@ if [ -z "$DANGER_RUN_CI_ON_HOST" ]; then
   fi
   echo "Creating $CI_IMAGE_NAME_TAG container to run in"
 
-  DOCKER_BUILD_CACHE_ARG=""
-  DOCKER_BUILD_CACHE_TEMPDIR=""
-  DOCKER_BUILD_CACHE_OLD_DIR=""
-  DOCKER_BUILD_CACHE_NEW_DIR=""
-  # If set, use an `docker build` cache directory on the CI host
-  # to cache docker image layers for the CI container image.
-  # This cache can be multiple GB in size. Prefixed with DANGER
-  # as setting it removes (old cache) files from the host.
-  if [ "$DANGER_DOCKER_BUILD_CACHE_HOST_DIR" ]; then
-    # Directory where the current cache for this run could be. If not existing
-    # or empty, "docker build" will warn, but treat it as cache-miss and continue.
-    DOCKER_BUILD_CACHE_OLD_DIR="${DANGER_DOCKER_BUILD_CACHE_HOST_DIR}/${CONTAINER_NAME}"
-    # Temporary directory for a newly created cache. We can't write the new
-    # cache into OLD_DIR directly, as old cache layers would not be removed.
-    # The NEW_DIR contents are moved to OLD_DIR after OLD_DIR has been cleared.
-    # This happens after `docker build`. If a task fails or is aborted, the
-    # DOCKER_BUILD_CACHE_TEMPDIR might be retained on the host. If the host isn't
-    # ephemeral, it has to take care of cleaning old TEMPDIR's up.
-    DOCKER_BUILD_CACHE_TEMPDIR="$(mktemp --directory ci-docker-build-cache-XXXXXXXXXX)"
-    DOCKER_BUILD_CACHE_NEW_DIR="${DOCKER_BUILD_CACHE_TEMPDIR}/${CONTAINER_NAME}"
-    DOCKER_BUILD_CACHE_ARG="--cache-from type=local,src=${DOCKER_BUILD_CACHE_OLD_DIR} --cache-to type=local,dest=${DOCKER_BUILD_CACHE_NEW_DIR},mode=max"
-  fi
-
   # Use buildx unconditionally
   # Using buildx is required to properly load the correct driver, for use with registry caching. Neither build, nor BUILDKIT=1 currently do this properly
   # shellcheck disable=SC2086
@@ -56,15 +33,6 @@ if [ -z "$DANGER_RUN_CI_ON_HOST" ]; then
       $DOCKER_BUILD_CACHE_ARG \
       "${BASE_READ_ONLY_DIR}"
 
-  if [ "$DANGER_DOCKER_BUILD_CACHE_HOST_DIR" ]; then
-    if [ -e "${DOCKER_BUILD_CACHE_NEW_DIR}/index.json" ]; then
-      echo "Removing the existing docker build cache in ${DOCKER_BUILD_CACHE_OLD_DIR}"
-      rm -rf "${DOCKER_BUILD_CACHE_OLD_DIR}"
-      echo "Moving the contents of ${DOCKER_BUILD_CACHE_NEW_DIR} to ${DOCKER_BUILD_CACHE_OLD_DIR}"
-      mv "${DOCKER_BUILD_CACHE_NEW_DIR}" "${DOCKER_BUILD_CACHE_OLD_DIR}"
-    fi
-  fi
-
   docker volume create "${CONTAINER_NAME}_ccache" || true
   docker volume create "${CONTAINER_NAME}_depends" || true
   docker volume create "${CONTAINER_NAME}_depends_sources" || true