[Bug libstdc++/57740] C++11 std::thread not usable with static linking

[roland at gnu dot org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=57740

--- Comment #5 from roland at gnu dot org ---
So my draft fix actually breaks the dynamic case.  For the unconditional calls,
weak is right in the shared library but strong is right in the static library.
But unlike normal libraries, libstdc++ goes out of its way to get compiled only
once, using PIC-compiled objects in the static library too.  So there is no
obvious way for gthr-posix.h to behave differently in the static and shared
cases, which is the only correct thing for it to do.