[Bug sanitizer/61547] Invalid sanitization of trailing byte in __builtin_strlen

[y.gribov at samsung dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=61547

--- Comment #1 from Yury Gribov <y.gribov at samsung dot com> ---
Created attachment 32964
  --> https://gcc.gnu.org/bugzilla/attachment.cgi?id=32964&action=edit
Proposed patch

Adding draft patch. I only ran Asan regression tests though (leaving for long
vacation today). Perhaps someone will have time to have a look at this.