Bump std++ (macOS build fix)
See this bug report from @jules on Mattermost: https://mattermost.mpi-sws.org/iris/pl/jarbufhxzfyefditii4xjig4qa.
See this bug report from @jules on Mattermost: https://mattermost.mpi-sws.org/iris/pl/jarbufhxzfyefditii4xjig4qa.