Fix mbtk_otad for dfota.

Change-Id: I928fba9e76a79c8223685a13b5b053b67496973e
diff --git a/mbtk/Makefile b/mbtk/Makefile
index fc87f45..905fa78 100755
--- a/mbtk/Makefile
+++ b/mbtk/Makefile
@@ -15,7 +15,7 @@
 DIRS += mbtk_rild mbtk_servicesd mbtk_sdk_ready
 endif
 
-DIRS += aboot-tiny mbtk_adbd mbtk_logd mbtk_utils mbtk_utils_linux mbtk_gnssd mbtk_rtpd
+DIRS += aboot-tiny mbtk_adbd mbtk_logd mbtk_utils mbtk_utils_linux mbtk_gnssd mbtk_rtpd mbtk_otad
 
 # Build test file.
 DIRS += test