GenericProject: Make dependency on CppTools optional

Especially in the light of the language server, the generic project is
currently the project one can use for language servers that require a
"project workspace".

Makes it possibly to run Qt Creator with
"-noload CppTools" if you still want to use generic
projects with some other language.

Change-Id: Ib9059289a2db4c44c0c1060a02fcdafacb885fbd
Reviewed-by: Nikolai Kosjar <nikolai.kosjar@qt.io>

src/plugins/cpptools/cppprojectupdater.h

@@ -25,6 +25,7 @@
 
 #pragma once
 
+#include "cppprojectupdaterinterface.h"
 #include "cpptools_global.h"
 #include "projectinfo.h"
 
@@ -35,7 +36,18 @@ namespace CppTools {
 
 class ProjectInfo;
 
-class CPPTOOLS_EXPORT CppProjectUpdater : public QObject
+// registered in extensionsystem's object pool for plugins with weak dependency to CppTools
+class CPPTOOLS_EXPORT CppProjectUpdaterFactory : public QObject
+{
+    Q_OBJECT
+public:
+    CppProjectUpdaterFactory();
+
+    // keep the namespace, for the type name in the invokeMethod call
+    Q_INVOKABLE CppTools::CppProjectUpdaterInterface *create();
+};
+
+class CPPTOOLS_EXPORT CppProjectUpdater : public QObject, public CppProjectUpdaterInterface
 {
     Q_OBJECT
 
@@ -43,8 +55,8 @@ public:
     CppProjectUpdater();
     ~CppProjectUpdater() override;
 
-    void update(const ProjectExplorer::ProjectUpdateInfo &projectUpdateInfo);
-    void cancel();
+    void update(const ProjectExplorer::ProjectUpdateInfo &projectUpdateInfo) override;
+    void cancel() override;
 
 private:
     void cancelAndWaitForFinished();