Add a gtest build target for the host.

Change-Id: Ib888e143c7f3c110a0596ce37f51138a4da31b5a
http://b/4584343
diff --git a/src/assembler_x86.h b/src/assembler_x86.h
index c1c16c7..e2445c5 100644
--- a/src/assembler_x86.h
+++ b/src/assembler_x86.h
@@ -5,6 +5,7 @@
 
 #include <stdint.h>
 #include <string.h>
+#include "src/assembler.h"
 #include "src/constants_x86.h"
 #include "src/macros.h"
 #include "src/utils.h"