http://gcc.gnu.org/bugzilla/show_bug.cgi?id=54630
--- Comment #14 from Jakub Jelinek <jakub at gcc dot gnu.org> 2012-11-20 20:19:58 UTC --- It is intentionally that way, so that one can fine tune the C++ libraries linked into the binary with --with-host-libstdcxx, but you are responsible for specifying there all the needed libraries. Don't use this configure option if you don't need it.
