build: Fix build when std::to_string is not available

Change-Id: If34fcebe17bd7e3de23655680957fa6e0df27676
Refs: #4393
diff --git a/daemon/fw/multicast-strategy.cpp b/daemon/fw/multicast-strategy.cpp
index f51693b..297f481 100644
--- a/daemon/fw/multicast-strategy.cpp
+++ b/daemon/fw/multicast-strategy.cpp
@@ -50,7 +50,7 @@
   }
   if (parsed.version && *parsed.version != getStrategyName()[-1].toVersion()) {
     BOOST_THROW_EXCEPTION(std::invalid_argument(
-      "MulticastStrategy does not support version " + std::to_string(*parsed.version)));
+      "MulticastStrategy does not support version " + to_string(*parsed.version)));
   }
   this->setInstanceName(makeInstanceName(name, getStrategyName()));
 }