[clang] [lldb] Serialize `#pragma redefine_extname` into precompiled headers. (PR #186755)

[Paul Kirth via cfe-commits]

================
@@ -0,0 +1,14 @@
+// Test this without pch.
----------------
ilovepi wrote:

```suggestion
/// Test this without pch.
```
Most tests use an extra comment symbol to convey that its a comment, so `///` for C/C++ or `;;` in LLVM IR. the `// COM:` directive is also a clear indicator that the line is a comment/informational.

https://github.com/llvm/llvm-project/pull/186755