Comment # 3 on bug 954362 from Egbert Eich

(In reply to Scru bbed from comment #2)
> When examining steamui.so with ldd and the same LD_LIBRARY_PATH steam.sh
> generates when using primusrun I found:
> 
> "./steamui.so:
> /home/llars/.local/share/Steam/ubuntu12_32/steam-runtime/i386/usr/lib/i386-
> linux-gnu/libstdc++.so.6: version `GLIBCXX_3.4.21' not found (required by
> /usr/lib/primus/libGL.so.1)".
> 
> The library it attempts to load is is shipped by steam and not compatible
> with primus.
> 
> Using symbolic links to the system-wide libstdc++.so.6 instead of the
> version shipped by steam gets steam running again.
> 
> For some games it is necessary to do the same thing with the 64-bit version
> (/home/llars/.local/share/Steam/ubuntu12_32/steam-runtime/amd64/usr/lib/
> x86_64-linux-gnu/libstdc++.so.6).
> 
> Some games ship their own libstdc++.so.6, making it necessary to apply this
> procedure to these games individually. (Portal2 is one of them)

Ok, thanks for finding this out. So this is a steam problem, not a bumblebee
one. 
Your mileage may vary as those libs are tightly bound to the ABI which in the
case of C++ is not really fixed. 
Still, checking with the oracle of google, one finds similar instructions quite
frequently on the net.
Let's pass it on the the package bugowners. Maybe they can make some adjustment
to the package to resolve this (as much as possible).