otautil: Export headers.

Test: mmma bootable/recovery
Change-Id: Ic01b68e2a394d578fc9fc09da2dabe9061b98122
diff --git a/Android.mk b/Android.mk
index c55771f..ac72bac 100644
--- a/Android.mk
+++ b/Android.mk
@@ -56,6 +56,7 @@
 LOCAL_MODULE := librecovery
 LOCAL_STATIC_LIBRARIES := \
     libminui \
+    libotautil \
     libvintf_recovery \
     libcrypto_utils \
     libcrypto \