[Bug libstdc++/86130] Expect SIGSEGV but program just silently exits

[redi at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=86130

--- Comment #3 from Jonathan Wakely <redi at gcc dot gnu.org> ---
Arguably crashing the program is more unfriendly.

We could add the nonnull attribute to the relevant ostream members, or add
assertions that can be optionally enabled, but I'm not convinced that crashing
is necessarily an improvement.