Fix the mac build

Change-Id: Id4a5c3b1a6fbebcf2079152c31a907536d7f950d
diff --git a/tools/incident_report/printer.cpp b/tools/incident_report/printer.cpp
index 1ab6bd8..8111b27 100644
--- a/tools/incident_report/printer.cpp
+++ b/tools/incident_report/printer.cpp
@@ -19,6 +19,7 @@
 #include <unistd.h>
 #include <stdlib.h>
 #include <string.h>
+#include <stdarg.h>
 
 #define INITIAL_BUF_SIZE (16*1024)