[clang] [CodeGen] Fix -fsanitize=array-bounds for __sized_by / _or_null pointers (PR #213795)

[Bill Wendling via cfe-commits]

https://github.com/bwendling approved this pull request.

Thanks for using a helper function! I definitely improves readability. :-)

https://github.com/llvm/llvm-project/pull/213795