[Bug libstdc++/59807] mutex misses destructor if non-function call initialization is used

[redi at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=59807

--- Comment #5 from Jonathan Wakely <redi at gcc dot gnu.org> ---
Yes, the copy in the sources needs to be fixed.  Does mingw-w64 always use
winpthread?