[Bug libstdc++/124554] [16 Regression] with newlib, libstdc++ build fails with 'variable or field ‘longjmp’ declared void' since r16-8118-gc362a260ca2032

[redi at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=124554

--- Comment #6 from Jonathan Wakely <redi at gcc dot gnu.org> ---
(In reply to Jonathan Wakely from comment #5)
> We can add a configure check for a working setjmp.h and then make the
> contents of <csetjmp> check a new autoconf macro.

But really, newlib should not be providing a setjmp.h header which can't even
be included.

If jmp_buf is not defined, then don't declare setjmp and longjmp either.