build: make precompiled headers more useful

This can reduce the compilation time of a release
build (without tests) by more than 40%

Refs: #5212
Change-Id: I977aff0c0c7becbfee8a8b55605b81d0c014829b
diff --git a/tools/ndn-autoconfig/main.cpp b/tools/ndn-autoconfig/main.cpp
index 2f8e561..3b30001 100644
--- a/tools/ndn-autoconfig/main.cpp
+++ b/tools/ndn-autoconfig/main.cpp
@@ -29,6 +29,7 @@
 #include <signal.h>
 #include <string.h>
 
+#include <boost/asio/signal_set.hpp>
 #include <boost/exception/diagnostic_information.hpp>
 #include <boost/program_options/options_description.hpp>
 #include <boost/program_options/parsers.hpp>