QmakeProjectManager: Merge QmakeManager into QmakeProjectManagerPrivate

No need for two manager type classes talking mostly to each other.

Change-Id: I82a52385df08dc4cddac2d294661341a79b86a4d
Reviewed-by: Christian Kandeler <christian.kandeler@qt.io>

src/plugins/qmakeprojectmanager/qmakeprojectmanagerplugin.h

@@ -27,6 +27,11 @@
 
 #include <extensionsystem/iplugin.h>
 
+namespace ProjectExplorer {
+class Project;
+class Node;
+} // ProjectExplorer
+
 namespace QmakeProjectManager {
 namespace Internal {
 
@@ -38,6 +43,8 @@ class QmakeProjectManagerPlugin final : public ExtensionSystem::IPlugin
 public:
     ~QmakeProjectManagerPlugin() final;
 
+    static void buildProduct(ProjectExplorer::Project *project, ProjectExplorer::Node *proFileNode);
+
 #ifdef WITH_TESTS
 private slots:
     void testQmakeOutputParsers_data();