test_image_util.sh: Copy DLC(s) for test images

build_dlc.py allows for filtering of DLC(s) built with preloading
capability and should be used to selectively copy DLC(s) that are
required for testing.

BUG=chromium:1037659
TEST=./build_image --board=$B --noenable_rootfs_verification test
Cq-Depend: chromium:1993689
Change-Id: I3e606db5b0da446d42f6f94621337877b7fa10d3
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/platform/crosutils/+/1994140
Tested-by: Jae Hoon Kim <kimjae@chromium.org>
Reviewed-by: Amin Hassani <ahassani@chromium.org>
Reviewed-by: Andrew Lassalle <andrewlassalle@chromium.org>
Reviewed-by: Chris McDonald <cjmcdonald@chromium.org>
Commit-Queue: Jae Hoon Kim <kimjae@chromium.org>
diff --git a/build_library/test_image_util.sh b/build_library/test_image_util.sh
index 0b5c1f0..2fbcab7 100755
--- a/build_library/test_image_util.sh
+++ b/build_library/test_image_util.sh
@@ -45,7 +45,8 @@
   # Move DLC images to the /var/cache directory. The dlc-images directory will
   # hold DLC(s) that dlcservice will leverage for testing/provisioning.
   sudo build_dlc --sysroot="${BOARD_ROOT}" \
-    --install-root-dir="${root_fs_dir}/var/cache/dlc-images"
+    --install-root-dir="${root_fs_dir}/var/cache/dlc-images" \
+    --preload
 
   unmount_image
   trap - EXIT