[Bug libstdc++/42734] trivial use of std::thread fails with "pure virtual method called"

[redi at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=42734

--- Comment #49 from Jonathan Wakely <redi at gcc dot gnu.org> ---
std::thread no longer uses shared_ptr on trunk, so no longer depends on atomics
and doesn't break if you mix objects compiled with and without native atomics,
e.g. mixing objects built for i386 with objects built for i686, or mixing
objects built for armv5 with objects built for armv7.