[clang] [clang][lex] Fix lexing malformed pragma within include directive (PR #138165)

[Aaron Ballman via cfe-commits]

================
@@ -0,0 +1,5 @@
+// RUN: %clang_cc1 %s -verify
----------------
AaronBallman wrote:

```suggestion
// RUN: %clang_cc1 -E %s -verify
```
This ensures we only run the preprocessing steps, which should still report the diagnostics.

https://github.com/llvm/llvm-project/pull/138165