Squashed 'third_party/flatbuffers/' content from commit acc9990ab

Change-Id: I48550d40d78fea996ebe74e9723a5d1f910de491
git-subtree-dir: third_party/flatbuffers
git-subtree-split: acc9990abd2206491480291b0f85f925110102ea
diff --git a/tests/docker/Dockerfile.testing.build_flatc_debian_stretch b/tests/docker/Dockerfile.testing.build_flatc_debian_stretch
new file mode 100644
index 0000000..197a555
--- /dev/null
+++ b/tests/docker/Dockerfile.testing.build_flatc_debian_stretch
@@ -0,0 +1,9 @@
+FROM debian:9.6-slim as base
+RUN apt -qq update >/dev/null
+RUN apt -qq install -y cmake make build-essential >/dev/null
+FROM base
+WORKDIR /code
+ADD . .
+RUN cmake -G "Unix Makefiles"
+RUN make flatc
+RUN ls flatc