message: Specify the C++ standard explicitly on MacOS when building Tink.
diff: @@ -5,7 +5,7 @@ cd ${KOKORO_ARTIFACTS_DIR}/git/tink
  echo "========================================================= Running cmake"
  cmake --version
  -cmake . -DTINK_BUILD_TESTS=ON
  +cmake . cmake . -DTINK_BUILD_TESTS=ON -DCMAKE_CXX_STANDARD=11
  echo "==================================================== Building with make"
  make -j8 all
  echo "===================================================== Testing with make"
  