ProjectExplorer: Use a data member for BuildStep::runInGuiThread

Change-Id: Ia219fcf595c05c6f1b82f420454bd906c6870ee7
Reviewed-by: Christian Kandeler <christian.kandeler@qt.io>

src/plugins/qbsprojectmanager/qbscleanstep.cpp

@@ -52,6 +52,7 @@ QbsCleanStep::QbsCleanStep(ProjectExplorer::BuildStepList *bsl) :
     ProjectExplorer::BuildStep(bsl, Constants::QBS_CLEANSTEP_ID)
 {
     setDisplayName(tr("Qbs Clean"));
+    setRunInGuiThread(true);
 }
 
 QbsCleanStep::~QbsCleanStep()
@@ -107,11 +108,6 @@ ProjectExplorer::BuildStepConfigWidget *QbsCleanStep::createConfigWidget()
     return new QbsCleanStepConfigWidget(this);
 }
 
-bool QbsCleanStep::runInGuiThread() const
-{
-    return true;
-}
-
 void QbsCleanStep::cancel()
 {
     if (m_job)