build: Experimental support to build using precompiled headers

This type of build needs to be explicitly enabled using --with-pch
configure option.

Change-Id: I02dc304187d54c3cf40f1d51b1b11b21f868e225
diff --git a/src/util/scheduler.cpp b/src/util/scheduler.cpp
index c13e070..388d5e7 100644
--- a/src/util/scheduler.cpp
+++ b/src/util/scheduler.cpp
@@ -4,6 +4,8 @@
  * See COPYING for copyright and distribution information.
  */
 
+#include "common.hpp"
+
 #include "scheduler.hpp"
 
 namespace ndn {