watch: Add missing functional include

std::function is not found with a GCC 7.2 runtime.

Change-Id: I6b1383703a3b741ed0e72ce3ea33bf44aed48f60
Tested: Built repository with GCC 7.2
Signed-off-by: Brad Bishop <bradleyb@fuzziesquirrel.com>

1 files changed, 1 insertions, 0 deletions

diff --git a/watch.cpp b/watch.cpp
index 2212e01a3..e076450d5 100644
--- a/watch.cpp
+++ b/watch.cpp
@@ -1,6 +1,7 @@
 #include <stdexcept>
 #include <cstddef>
 #include <cstring>
+#include <functional>
 #include <string>
 #include <sys/inotify.h>
 #include <unistd.h>