[Bug libstdc++/96657] [9/10/11 Regression] libsupc++.a missing required functions from src/c++98/atomicity.cc when atomic builtins are not supported

[redi at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=96657

--- Comment #3 from Jonathan Wakely <redi at gcc dot gnu.org> ---
Yes, I think that's what we need to do.