adapt a codegen test for llvm 19 No functional changes intended. Found by our experimental rust + LLVM @ HEAD bot: https://buildkite.com/llvm-project/rust-llvm-integrate-prototype/builds/27747#018f2570-018c-4b12-9c5a-38cf81453683/957-965 `@rustbot` label: +llvm-main r? `@durin42`