[llvm] [DataFlowSanitizer] Properly add ext attributes on arguments as needed. (PR #225443)

[Eli Friedman via llvm-commits]

efriedma-quic wrote:

(Note https://llvm.org/docs/AIToolPolicy.html requires explicitly noting AI-generated code in the commit message.)

https://github.com/llvm/llvm-project/pull/225443