fixup: grab all of array for cli11

Fixup missed use of ${CMAKE_FLAGS} instead of ${CMAKE_FLAGS[@]}.

Change-Id: I744685e4645608d1aefc9b83cc27fb797d804952
Signed-off-by: Patrick Venture <venture@google.com>
diff --git a/build-unit-test-docker.sh b/build-unit-test-docker.sh
index 3f1870d..80e51c2 100755
--- a/build-unit-test-docker.sh
+++ b/build-unit-test-docker.sh
@@ -212,7 +212,7 @@
 cd CLI11-* && \
 mkdir build && \
 cd build && \
-cmake ${CMAKE_FLAGS} -DCLI11_TESTING=OFF -DCLI11_EXAMPLES=OFF .. && \
+cmake ${CMAKE_FLAGS[@]} -DCLI11_TESTING=OFF -DCLI11_EXAMPLES=OFF .. && \
 make -j$(nproc) && \
 make install