Include libavb in static libraries

Bug: 31264231
Test: compile
Change-Id: I1d84f7aa67a0ed31f2b6400cf1c9567bf503295a
diff --git a/Android.mk b/Android.mk
index d9f8753..1b38393 100644
--- a/Android.mk
+++ b/Android.mk
@@ -67,6 +67,7 @@
 	libsquashfs_utils \
 	libscrypt_static \
 	libbatteryservice \
+	libavb \
 
 vold_conlyflags := -std=c11
 vold_cflags := -Werror -Wall -Wno-missing-field-initializers -Wno-unused-variable -Wno-unused-parameter