Resolve lint warning about converting unsigned to signed (NFC)

FileOffset is unsigned while getLocWithOffset() requires a signed value.

Author: salman-javed-nz

clang-tools-extra/clang-tidy/ClangTidyDiagnosticConsumer.cpp

@@ -193,7 +193,8 @@ DiagnosticBuilder ClangTidyContext::diag(const ClangTidyError &Error) {
       SM.getFileManager().getFile(Error.Message.FilePath);
   FileID ID = SM.getOrCreateFileID(*File, SrcMgr::C_User);
   SourceLocation FileStartLoc = SM.getLocForStartOfFile(ID);
-  SourceLocation Loc = FileStartLoc.getLocWithOffset(Error.Message.FileOffset);
+  SourceLocation Loc = FileStartLoc.getLocWithOffset(
+      static_cast<SourceLocation::IntTy>(Error.Message.FileOffset));
   return diag(Error.DiagnosticName, Loc, Error.Message.Message,
               static_cast<DiagnosticIDs::Level>(Error.DiagLevel));
 }