Add missing include that was causing Windows builds breaks.

Change-Id: Iccdbcb1eaee50ff93797fefdbae4318d21a187dd
diff --git a/common/log.cc b/common/log.cc
index 4394df9..34adf53 100644
--- a/common/log.cc
+++ b/common/log.cc
@@ -6,6 +6,7 @@
 
 #include <cstdarg>
 #include <cstdio>
+#include <memory>
 
 namespace tonic {