travis: Run CPP tests

tests/travis/run_test.sh

@@ -88,3 +88,11 @@ if [ ${TASK} == "cmake_test" ]; then
     cmake ..
     make
 fi
+
+if [ ${TASK} == "cpp_test" ]; then
+    set -e
+    make -f dmlc-core/scripts/packages.mk gtest
+    echo "TEST_COVER=1" >> config.mk
+    echo "GTEST_PATH="${CACHE_PREFIX} >> config.mk
+    make check
+fi