C++ competitive setup on OS X
cannot be included because of reasons. To fix:
Go to /usr/local/include, create /bin folder and inside create a stdc++.h file and copy https://gist.github.com/sachin-kmr/ee03a0d07be6fcfd439b49307a12f7ed inside.
Edit: After the recent OS update, you also need to re-instantiate yourself as a developer
