[llvm] [PDB][NativeSession] Use better error code for invalid format (PR #167885)

[Alexandre Ganea via llvm-commits]

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@@ -87,6 +87,20 @@ Error NativeSession::createFromPdb(std::unique_ptr<MemoryBuffer> Buffer,
   return Error::success();
 }
 
+static Error validatePdbMagic(StringRef PdbPath) {
+  file_magic Magic;
+  auto EC = identify_magic(PdbPath, Magic);
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aganea wrote:

You can write `if (auto EC = ... )` to make it shorter.

https://github.com/llvm/llvm-project/pull/167885