[Bug sanitizer/64984] [5 Regression] ICE in check_noexcept_t with ubsan

[larsbj at gullik dot net]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=64984

--- Comment #4 from Lars Gullik Bjønnes <larsbj at gullik dot net> ---
(In reply to Jakub Jelinek from comment #3)
> Created attachment 34710 [details]
> gcc5-pr64984.patch
> 
> Untested fix.

This seems to fix ICE, but I have at least one more that needs tracking down,
also related to -fsanitize=undefined, but not to -fsanitize=vptr.
(and a hang with -fsanitize=address and heap-use-after-free reporting.)

I'll create separate bugs for those.