[clang] [clang] Canonicalizing `-include-pch` input in the Frontend (PR #180065)

[Cyndy Ishida via cfe-commits]

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@@ -6117,6 +6120,9 @@ ASTFileSignature ASTWriter::WriteASTCore(Sema *SemaPtr, StringRef isysroot,
 
         endian::Writer LE(Out, llvm::endianness::little);
         LE.write<uint8_t>(static_cast<uint8_t>(M.Kind));
+        // FIXME: Storing Name as just a string does not handle relocatable
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cyndyishida wrote:

This isn't strictly true, right? It's only an issue if the `Name`  is a pch path. I would change this to 

```
// FIXME:  If `Name` captures PCH path, it will not support relocatable AST.  
```

https://github.com/llvm/llvm-project/pull/180065