Qmake: Fix a warning

qmakeevaluator.cpp:297:13: warning: this statement may fall through [-Wimplicit-fallthrough=]

Change-Id: I157ba28e438b623d41dc7444c1381ecd649d3425
Reviewed-by: Eike Ziller <eike.ziller@qt.io>

src/shared/proparser/qmakeevaluator.cpp

@@ -295,7 +295,8 @@ ProStringList QMakeEvaluator::split_value_list(QStringView vals, int source)
                     --x;
                 }
             }
-            // fallthrough
+            hadWord = true;
+            break;
         default:
             hadWord = true;
             break;