tests/docker: Add flex/bison to `debian-all-test`

Adds flex/bison to the debian-all-test-cross container which was missed
in the previous CI patch. These dependencies are required by the
idef-parser patchset for target/hexagon.

Signed-off-by: Anton Johansson <anjo@rev.ng>
Signed-off-by: Alex Bennée <alex.bennee@linaro.org>
Reviewed-by: Thomas Huth <thuth@redhat.com>
Message-Id: <20221011173229.57909-1-anjo@rev.ng>
Message-Id: <20221027183637.2772968-4-alex.bennee@linaro.org>

tests/docker/dockerfiles/debian-all-test-cross.docker

@@ -20,8 +20,10 @@ RUN export DEBIAN_FRONTEND=noninteractive && \
 # Add extra build tools and as many cross compilers as we can for testing
 RUN DEBIAN_FRONTEND=noninteractive eatmydata \
         apt install -y --no-install-recommends \
+        bison \
         ccache \
         clang  \
+        flex \
         git \
         ninja-build \
         gcc-aarch64-linux-gnu \