Reland "CTR: add xxd to env"

This is a reland of commit ab1a0551349821afc103190af979d220d177651b

Original change's description:
> CTR: add xxd to env
>
> BUG=b:256558862
> TEST=./build-dockerimages.py and docker run <image> xxd
>
> Change-Id: If4a2d61914c558fde57cfed55c7091c9f5ef60a5
> Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/platform/dev-util/+/3997876
> Auto-Submit: Derek Beckett <dbeckett@chromium.org>
> Reviewed-by: Jaques Clapauch <jaquesc@google.com>
> Commit-Queue: Jaques Clapauch <jaquesc@google.com>
> Tested-by: Derek Beckett <dbeckett@chromium.org>

Bug: b:256558862
Change-Id: I03b2e9c17b0d0bbb80342d159cd4662b5108c586
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/platform/dev-util/+/3998132
Commit-Queue: Derek Beckett <dbeckett@chromium.org>
Tested-by: Derek Beckett <dbeckett@chromium.org>
Reviewed-by: Jaques Clapauch <jaquesc@google.com>

src/chromiumos/test/dockerfiles/cros-test/Dockerfile

diff --git a/src/chromiumos/test/dockerfiles/cros-test/Dockerfile b/src/chromiumos/test/dockerfiles/cros-test/Dockerfile
index 08a890b..1ba6614 100644
--- a/src/chromiumos/test/dockerfiles/cros-test/Dockerfile
+++ b/src/chromiumos/test/dockerfiles/cros-test/Dockerfile
@@ -17,7 +17,8 @@
       sudo \
       unzip \
       openjdk-11-jdk \
-      wget
+      wget \
+      xxd
 
 # grab gsutil
 RUN echo \