[!damo!spiderman]

Yep the way you're doing it isn't going to work, you're just enabled that version of gcc for the session but you're not actually trying to use gcc in this situation you're just trying to use one of the libraries that gcc has which isn't going to be put in the usual /usr/lib directory in this case.

What you'll want to do is locate libstdc++.so file from the devtoolset you installed and copy it to /usr/lib/ and then link to it with

ln -s libstdc++.so.6 libstdc++.so.6.*(whatever the file is called)