[Bug libstdc++/123167] to_chars(long double) produces rubbish with -mlong-double-64

[redi at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=123167

--- Comment #6 from Jonathan Wakely <redi at gcc dot gnu.org> ---
Putting it another way, the platform ABI says that long double is 80-bit on
x86_64. If you change that, you are creating a new, incompatible platform. At
that point, it's your job to provide a suitable libc (you can't use glibc) and
to rebuild libstdc++.so for your custom platform.