[clang] [Clang][CodeGen] Fix C++20 NTTP object field indexing (PR #204174)

[Eli Friedman via cfe-commits]

================
@@ -0,0 +1,44 @@
+// RUN: %clang_cc1 -triple=x86_64-unknown-linux-gnu -std=c++20 -O1 \
----------------
efriedma-quic wrote:

We usually try to avoid using -O1 in clang codegen tests because it ties the test to specific optimizer behaviors.  We occasionally do it in specific cases where it's hard to read the CHECK lines, or the optimizer behavior is important, but I don't think that applies here.

https://github.com/llvm/llvm-project/pull/204174