Fix build when fwrite() is declared with attribute warn_unused_result

Task-number: QTBUG-33921
Change-Id: I58dded1f54239e4c5cfd5f4f5c1655dbf879b2c8
Reviewed-by: Olivier Goffart <ogoffart@woboq.com>
Reviewed-by: Thiago Macieira <thiago.macieira@intel.com>

src/tools/moc/generator.cpp

@@ -310,7 +310,7 @@ void Generator::generateCode()
                 int escapeLen = lengthOfEscapeSequence(s, backSlashPos);
                 spanLen = qBound(spanLen, backSlashPos + escapeLen - idx, s.length() - idx);
             }
-            fwrite(s.constData() + idx, 1, spanLen, out);
+            fprintf(out, "%.*s", spanLen, s.constData() + idx);
             idx += spanLen;
             col += spanLen;
         }