[Bug libstdc++/63829] _Lock_policy used in thread.cc can cause incompatibilities with binaries using different -mcpu

[redi at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=63829

--- Comment #5 from Jonathan Wakely <redi at gcc dot gnu.org> ---
(In reply to Aaron Graham from comment #3)
> I've solved this problem in my own setup by building the toolchain and
> application binaries with the same -mcpu.
> 
> A more general solution might be to move more code out of places like
> thread.cc and into the headers.

I think the right solution is to determine the lock policy when GCC is
configured and set it once and not have it change at compile-time based on
flags such as -mcpu.