[clang] [NFC] Optimize file kind determination (PR #139492)

[via cfe-commits]

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@@ -1529,6 +1529,15 @@ class SourceManager : public RefCountedBase<SourceManager> {
     return Filename == "<scratch space>";
   }
 
+  /// Returns whether \p Loc is located in a built-ins or command line sources.
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cor3ntin wrote:

```suggestion
  /// Returns whether \p Loc is located in a built-in or command line source.
```

https://github.com/llvm/llvm-project/pull/139492