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

[Jan Svoboda via cfe-commits]

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@@ -0,0 +1,29 @@
+// Testing `-include-pch` canoniclaization.
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jansvoboda11 wrote:

```suggestion
// Testing `-include-pch` canonicalization.
```

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