use valSeen since it results in unused warning otherwise

upstream commits:
9dc7f84839

Signed-off-by: Ivailo Monev <xakepa10@gmail.com>

src/test/qbenchmarkvalgrind.cpp

@@ -122,7 +122,8 @@ qint64 QBenchmarkValgrindUtils::extractResult(const QString &fileName)
             break;
         }
     }
-    Q_ASSERT(valSeen);
+    if (!valSeen)
+        qFatal("failed to extract result");
     return val;
 }