[Bug sanitizer/64888] ubsan doesn't work with openmp

[mpolacek at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=64888

--- Comment #2 from Marek Polacek <mpolacek at gcc dot gnu.org> ---
Started looking into this.  Seems that we should handle specially those
artificial ubsan decls such as *.Lubsan_data in omp_default_clause, i.e. treat
them as shared?  But I hardly know what I'm talking about; inviting Jakub to
comment.