Forces CI to use clang-3.9 (#135)

* Forces CI to use clang-3.9

contrib/docker/Makefile

@@ -53,7 +53,10 @@ check_cpu: build_ngraph_cpp_cpu
 	chmod ug+rwx ${DIR}/BUILD
 	# Need to use /tmp/ngraph-cpp-test/BUILD, because running as user
 	# Can't use /root/ngraph-cpp-test/BUILD, because /root not accessible to user
-	docker run --rm --user ${CALLER_UID}:${CALLER_GID} ${DOCKER_RUN_ENV} ${VOLUME} -w /tmp/ngraph-cpp-test/BUILD -t ngraph_cpp_cpu:${BUILD_VERSION} sh -c "cmake .. ; make check"
+	docker run \
+	    --rm --user ${CALLER_UID}:${CALLER_GID} \
+	    ${DOCKER_RUN_ENV} ${VOLUME} -w /tmp/ngraph-cpp-test/BUILD -t ngraph_cpp_cpu:${BUILD_VERSION} \
+	    sh -c "cmake -DCMAKE_CXX_COMPILER=clang++-3.9 -DCMAKE_C_COMPILER=clang-3.9 .. ; env VERBOSE=1 make check"
 	# update the files to be owned by the calling user instead of root, to avoid docker mount problems with file ownership
 	docker run --rm ${VOLUME} \
 	--env MY_UID=${CALLER_UID} \