CMakePM: Compress empty project folders

This way the user doesn't have to click and click in oder to get to the
contained file nodes.

Fixes: QTCREATORBUG-32217
Change-Id: If75a04ea22f710c71582f7f9aacfb0324019066a
Reviewed-by: Christian Kandeler <christian.kandeler@qt.io>

src/plugins/cmakeprojectmanager/fileapidataextractor.cpp

@@ -1021,6 +1021,7 @@ FileApiQtcData extractData(const QFuture<void> &cancelFuture, FileApiData &input
     auto rootProjectNode = generateRootProjectNode(cancelFuture, data, sourceDir, buildDir);
     if (cancelFuture.isCanceled())
         return {};
+    rootProjectNode.get()->compress();
     ProjectTree::applyTreeManager(rootProjectNode.get(), ProjectTree::AsyncPhase); // QRC nodes
     result.rootProjectNode = std::move(rootProjectNode);