[clang] fix bug that undefined internal is a warning only for -pedantic-errors (PR #98016)

[Aaron Ballman via cfe-commits]

================
@@ -0,0 +1,10 @@
+// RUN: %clang_cc1 -fsyntax-only -verify %s -pedantic-errors
----------------
AaronBallman wrote:

```suggestion
// RUN: %clang_cc1 -fsyntax-only -verify %s -Wno-pointer-arith -pedantic-errors
```

https://github.com/llvm/llvm-project/pull/98016