trying to fix boost variant by adding a define

Former-commit-id: 91c98c91a0

src/generator/NextStateGenerator.cpp

@@ -12,6 +12,8 @@
 #include "src/utility/macros.h"
 #include "src/exceptions/InvalidSettingsException.h"
 
+#define BOOST_VARIANT_USE_RELAXED_GET_BY_DEFAULT
+
 namespace storm {
     namespace generator {