QMakeProjectManager: Avoid usage of global thread pool.

Using a global thread pool does not really make sense, since we do not
want to block any completely unrelated task. But the qmake project
manager still wants to limit the number of simultaneous threads without
managing that itself. A shared thread pool in project explorer sounds
like a sensible middle ground.

Change-Id: Ide6fd546a56e8f4896c387168513b608dfe7e3e8
Reviewed-by: Tobias Hunger <tobias.hunger@theqtcompany.com>

src/plugins/qmakeprojectmanager/qmakenodes.cpp

@@ -1800,7 +1800,9 @@ void QmakeProFileNode::asyncUpdate()
         m_readerExact->setExact(false);
     m_parseFutureWatcher.waitForFinished();
     EvalInput input = evalInput();
-    QFuture<EvalResult *> future = QtConcurrent::run(&QmakeProFileNode::asyncEvaluate, this, input);
+    QFuture<EvalResult *> future = Utils::runAsync<EvalResult *>(ProjectExplorerPlugin::sharedThreadPool(),
+                                                                 &QmakeProFileNode::asyncEvaluate,
+                                                                 this, input);
     m_parseFutureWatcher.setFuture(future);
 }