[AMDGPU] Print metadata on error

[Flakebi]

Summary

If the metadata is valid yaml, we can print it, even if it failed
validation. That makes it easier to debug any wrong metadata.

[jhenderson]

Seems like a reasonable idea. Test case?

llvm/tools/llvm-readobj/ELFDumper.cpp

static AMDGPUNote getAMDGPUNote(uint32_t NoteType, ArrayRef<uint8_t> Desc) {
   case ELF::NT_AMDGPU_METADATA: {
     StringRef MsgPackString =
         StringRef(reinterpret_cast<const char *>(Desc.data()), Desc.size());
     msgpack::Document MsgPackDoc;
     if (!MsgPackDoc.readFromBlob(MsgPackString, /*Multi=*/false))
       return {"AMDGPU Metadata", "Invalid AMDGPU Metadata"};
 
     AMDGPU::HSAMD::V3::MetadataVerifier Verifier(true);
+    std::string HSAMetadataString;
     if (!Verifier.verify(MsgPackDoc.getRoot()))
-      return {"AMDGPU Metadata", "Invalid AMDGPU Metadata"};
+      HSAMetadataString = "Invalid AMDGPU Metadata\n";
 
-    std::string HSAMetadataString;
     raw_string_ostream StrOS(HSAMetadataString);
     MsgPackDoc.toYAML(StrOS);
 
     return {"AMDGPU Metadata", StrOS.str()};
   }
   }
 }