http://gcc.gnu.org/bugzilla/show_bug.cgi?id=52680
--- Comment #1 from Jonathan Wakely <redi at gcc dot gnu.org> 2012-03-23 12:45:48 UTC --- Don't define that manually, you should configure gcc with --enable-libstdccxx-time instead. We need to revisit the configure tests for nanosleep and sched_yield, as they are always available on some platforms, so we might be able to make --enable-libstdcxx-time the default, or make the configure checks more finegrained.
