Add a missing header for bitpacking_test

Change-Id: I6d4544018b0c02c97a00d026dc1081d3e7db398e
Signed-off-by: Austin Schuh <austin.schuh@bluerivertech.com>
diff --git a/aos/util/bitpacking_test.cc b/aos/util/bitpacking_test.cc
index 80d1977..087c719 100644
--- a/aos/util/bitpacking_test.cc
+++ b/aos/util/bitpacking_test.cc
@@ -1,5 +1,6 @@
 #include "aos/util/bitpacking.h"
 
+#include <array>
 #include <cstdint>
 
 #include "gtest/gtest.h"