Restore functional DONT_USE_BUILTIN_SETJMP support

[Eric Botcazou]

> This cause
> 
> % /opt/gcc/gcc8w/bin/g++ -std=c++11 -O2 -fnon-call-exceptions
> /opt/gcc/work/gcc/testsuite/g++.dg/pr62079.C -c -m32
> /opt/gcc/work/gcc/testsuite/g++.dg/pr62079.C: In function 'int main()':
> /opt/gcc/work/gcc/testsuite/g++.dg/pr62079.C:78:1: error: non-cold basic
> block 5 reachable only by paths crossing the cold partition }
>  ^
> during RTL pass: split2
> /opt/gcc/work/gcc/testsuite/g++.dg/pr62079.C:78:1: internal compiler error:
> verify_flow_info failed
> 
> on x86_64-apple-darwin16.

Really sure?  The patch is a no-op except for IA-64 and Aarch64.

-- 
Eric Botcazou