We get more similar linking errors elsewhere anyway. We would need a
more generic fix. As for now, just apparently not possible to build
with the LLVM g++ from Xcode 4. Use g++-4.2 / gcc-4.2 if you want ot
use Xcode 4. But note that for Xcode 4.2, you might need to do:

ln -s i686-apple-darwin10 /Developer/SDKs/MacOSX10.6.sdk/usr/lib/gcc/i686-apple-darwin11

This reverts commit f3e10529.