Utils: Make the second parameter to LayoutBuilder::attach() an enum

More explicit and more potential options (e.g. "treat grid as form")
than a bool.

Change-Id: I89413efe30410160c38b0e524ba64288dde2332e
Reviewed-by: Eike Ziller <eike.ziller@qt.io>

src/plugins/qmakeprojectmanager/qmakestep.cpp

@@ -529,7 +529,7 @@ QWidget *QMakeStep::createConfigWidget()
     builder.addRow(m_userArgs);
     builder.addRow(m_effectiveCall);
     builder.addRow({abisLabel, abisListWidget});
-    auto widget = builder.emerge(false);
+    auto widget = builder.emerge(Layouting::WithoutMargins);
 
     qmakeBuildConfigChanged();