Use StringBuilder for GetString/GetStringWithArgs, as per upstream

Update dependent code as required

src/ship_gui.cpp

@@ -74,7 +74,6 @@ void DrawShipDetails(const Vehicle *v, const Rect &r)
 	if (v->Next() != nullptr) {
 		CargoArray max_cargo{};
 		StringID subtype_text[NUM_CARGO];
-		char capacity[512];
 
 		memset(subtype_text, 0, sizeof(subtype_text));
 
@@ -86,23 +85,18 @@ void DrawShipDetails(const Vehicle *v, const Rect &r)
 			}
 		}
 
-		GetString(capacity, STR_VEHICLE_DETAILS_TRAIN_ARTICULATED_RV_CAPACITY, lastof(capacity));
+		std::string capacity = GetString(STR_VEHICLE_DETAILS_TRAIN_ARTICULATED_RV_CAPACITY);
 
 		bool first = true;
 		for (CargoID i = 0; i < NUM_CARGO; i++) {
 			if (max_cargo[i] > 0) {
-				char buffer[128];
-
+				if (!first) capacity += ", ";
 				SetDParam(0, i);
 				SetDParam(1, max_cargo[i]);
-				GetString(buffer, STR_JUST_CARGO, lastof(buffer));
-
-				if (!first) strecat(capacity, ", ", lastof(capacity));
-				strecat(capacity, buffer, lastof(capacity));
+				GetString(StringBuilder(capacity), STR_JUST_CARGO);
 
 				if (subtype_text[i] != 0) {
-					GetString(buffer, subtype_text[i], lastof(buffer));
-					strecat(capacity, buffer, lastof(capacity));
+					GetString(StringBuilder(capacity), subtype_text[i]);
 				}
 
 				first = false;