libstdc++.so.6 in base 9.2 system collides with libstdc++.so.6 in gcc47

[Yuri]

After the ports update my qbittorrent fails due to this collision:
$ qbittorrent
/usr/lib/libstdc++.so.6: version GLIBCXX_3.4.15 required by 
/usr/local/lib/libtorrent-rasterbar.so.7 not found

I guess, all packages depending on gcc47 libs would likely fail the same 
way.

gcc probably forgot to bump so revision.

The workaround is to run with LD_LIBRARY_PATH=/usr/local/lib/gcc47
But what is the general solution for this?

Yuri