[Bug libstdc++/71684] Memory leak with std::mutex and std::lock_guard on freebsd

[christian.prochaska--- via Gcc-bugs]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=71684

--- Comment #10 from Christian Prochaska <christian.procha...@genode-labs.com> 
---
std::__condvar always calls __gthread_cond_destroy() even if
__GTHREAD_COND_INIT is used. So, it's handled differently there than in
std::__mutex_base.