[clang] Make -frewrite-includes put an endif at the end of the included text (PR #67613)

[Erich Keane via cfe-commits]

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@@ -332,12 +346,14 @@ void InclusionRewriter::CommentOutDirective(Lexer &DirectiveLex,
     // OutputContentUpTo() would not output anything anyway.
     return;
   }
-  OS << "#if 0 /* expanded by -frewrite-includes */" << MainEOL;
+  OS << "#if 0 /* " << getIncludedFileName(Inc)
----------------
erichkeane wrote:

I DO think there is at least a good attempt that could be made to get a unique set of names for each (perhaps a stringify of the path, ala how `#line` does it?), but I think this is a good stand-alone feature here.

One thing I MIGHT suggest anyway though is replacing the '0' with `defined(__CLANG_REWRITTEN_INCLUDES)`, so that turning on the `#include` version would be trivial.

I might also suggest for certain lines, `defined(__CLANG_REWRITTEN_SYSTEM_INCLUDES)` such that only the system headers are used from the test machine.

So that is, a system header would be:

```#if defined(__CLANG_REWRITTEN_INCLUDES) || defined(__CLANG_REWRITTEN_SYSTEM_INCLUDES) /* vector expanded by -frewrite-includes */```

 



https://github.com/llvm/llvm-project/pull/67613