otautil: Export headers.

Test: mmma bootable/recovery
Change-Id: Ic01b68e2a394d578fc9fc09da2dabe9061b98122
diff --git a/otautil/DirUtil.cpp b/otautil/DirUtil.cpp
index fffc822..61c8328 100644
--- a/otautil/DirUtil.cpp
+++ b/otautil/DirUtil.cpp
@@ -14,7 +14,7 @@
  * limitations under the License.
  */
 
-#include "DirUtil.h"
+#include "otautil/DirUtil.h"
 
 #include <dirent.h>
 #include <errno.h>