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/QtProjectWizardContentJavaStandard.cpp

@@ -1,5 +1,7 @@
 #include "QtProjectWizardContentJavaStandard.h"
 
+#if BUILD_JAVA_LANGUAGE_PACKAGE
+
 #include <QComboBox>
 #include <QLabel>
 
@@ -46,3 +48,5 @@ void QtProjectWizardContentJavaStandard::save()
 		m_sourceGroupSettings->setJavaStandard(m_standard->currentText().toStdWString());
 	}
 }
+
+#endif // BUILD_JAVA_LANGUAGE_PACKAGE