Fix build (missing #include).

Change-Id: Icafc2289d1320f2cd41e8756363240268780d8b8
diff --git a/tests/nusensors/nusensors.cpp b/tests/nusensors/nusensors.cpp
index 731fa09..29e2069 100644
--- a/tests/nusensors/nusensors.cpp
+++ b/tests/nusensors/nusensors.cpp
@@ -15,6 +15,7 @@
  */
 
 #include <stdint.h>
+#include <string.h>
 #include <sys/cdefs.h>
 #include <sys/types.h>