[Bug sanitizer/81021] stack-use-after-scope false positive error with exceptions

[avi@cloudius-systems.com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=81021

--- Comment #28 from Avi Kivity <avi@cloudius-systems.com> ---
It's a combination of several things:

1. We use antlr to generate a parser. The generated code allocates many local
variables in the same function
2. use-after-scope disabled -fstack-reuse=all
3. ASAN is quite liberal with stack padding
4. We also use user-level threads with just 128k of stack

The combination of all four overflowed our poor stack.