CMake: Server-mode: Use sourceDirectory directly

Change-Id: I0929ea86e24a8f1aa4dbfc5d41421127accefe33
Reviewed-by: Tim Jenssen <tim.jenssen@qt.io>

src/plugins/cmakeprojectmanager/servermodereader.cpp

@@ -519,7 +519,7 @@ QSet<Node *> ServerModeReader::updateCMakeLists(CMakeListsNode *root,
 {
     QSet<Node *> usedNodes;
 
-    const QDir baseDir = QDir(root->filePath().parentDir().toString());
+    const QDir baseDir = QDir(m_parameters.sourceDirectory.toString());
 
     QHash<QString, FileNode *> nodeHash;
     for (FileNode *cm : cmakeLists) {