ProjectExplorer: Use sessionmanager to set active target

Change-Id: I1e3abe473dc5eb68589de5b0b5d6ec8ea361febf
Reviewed-by: Tim Jenssen <tim.jenssen@qt.io>

src/plugins/projectexplorer/project.cpp

@@ -259,7 +259,7 @@ void Project::addTarget(std::unique_ptr<Target> &&t)
 
     // check activeTarget:
     if (!activeTarget())
-        setActiveTarget(pointer);
+        SessionManager::setActiveTarget(this, pointer, SetActive::Cascade);
 }
 
 bool Project::removeTarget(Target *target)