[clang][NFC] silences warnings

* removes unused data member `OS` from `SARIFDiagnostic`
* flags `Filename` variable as currently unused

This is a follow-up to D131632.

Author: abrahamcd

clang/include/clang/Frontend/SARIFDiagnostic.h

@@ -55,8 +55,6 @@ class SARIFDiagnostic : public DiagnosticRenderer {
                                   StringRef ModuleName) override;
 
 private:
-  raw_ostream &OS;
-
   // Shared between SARIFDiagnosticPrinter and this renderer.
   SarifDocumentWriter *Writer;
 

clang/lib/Frontend/SARIFDiagnostic.cpp

@@ -33,7 +33,7 @@ namespace clang {
 SARIFDiagnostic::SARIFDiagnostic(raw_ostream &OS, const LangOptions &LangOpts,
                                  DiagnosticOptions *DiagOpts,
                                  SarifDocumentWriter *Writer)
-    : DiagnosticRenderer(LangOpts, DiagOpts), OS(OS), Writer(Writer) {}
+    : DiagnosticRenderer(LangOpts, DiagOpts), Writer(Writer) {}
 
 // FIXME(llvm-project/issues/57323): Refactor Diagnostic classes.
 void SARIFDiagnostic::emitDiagnosticMessage(
@@ -71,7 +71,8 @@ SarifResult SARIFDiagnostic::addLocationToResult(
     FileID FID = Loc.getFileID();
     if (FID.isValid()) {
       if (const FileEntry *FE = Loc.getFileEntry()) {
-        emitFilename(FE->getName(), Loc.getManager());
+        [[gnu::unused]] llvm::StringRef Filename =
+            emitFilename(FE->getName(), Loc.getManager());
         // FIXME(llvm-project/issues/57366): File-only locations
       }
     }