Add missing headers for compilation on x86 targets

Change-Id: I5f4dc797b353a0f01fa00d38375ec303bf863254
diff --git a/toolbox/notify.c b/toolbox/notify.c
index b1761d2..c983ed5 100644
--- a/toolbox/notify.c
+++ b/toolbox/notify.c
@@ -3,6 +3,7 @@
 #include <string.h>
 #include <stdint.h>
 #include <fcntl.h>
+#include <unistd.h>
 #include <sys/ioctl.h>
 #include <sys/inotify.h>
 #include <errno.h>