add verbose flag

Author: pcmoritz

ci/travis_script_cpp.sh

@@ -23,7 +23,7 @@ source $TRAVIS_BUILD_DIR/ci/travis_env_common.sh
 
 pushd $CPP_BUILD_DIR
 
-PATH=$ARROW_BUILD_TYPE:$PATH ctest -j2 --output-on-failure -L unittest
+PATH=$ARROW_BUILD_TYPE:$PATH ctest -j2 --verbose --output-on-failure -L unittest
 
 popd