build: allow to disable language support in cmake

* in addition: add unloadable sourcegroup to visualize, load and save information when loading a project that contains source groups that are not supported by the build

src/lib_gui/qt/project_wizard/content/path/QtProjectWizardContentPathCxxPch.cpp

@@ -1,5 +1,7 @@
 #include "QtProjectWizardContentPathCxxPch.h"
 
+#if BUILD_CXX_LANGUAGE_PACKAGE
+
 #include <QMessageBox>
 
 #include "IndexerCommandCxx.h"
@@ -108,3 +110,5 @@ std::shared_ptr<SourceGroupSettings> QtProjectWizardContentPathCxxPch::getSource
 {
 	return m_settings;
 }
+
+#endif // BUILD_CXX_LANGUAGE_PACKAGE