Mark libmodpb64 as recovery_available for update_engine_sideload

Test: build update_engine_sideload
Change-Id: Ibdf0d789f9cbdfe4c4f8583ee74e835ad2609ee9
diff --git a/Android.bp b/Android.bp
index ee26dad..064aa64 100644
--- a/Android.bp
+++ b/Android.bp
@@ -15,6 +15,7 @@
 cc_library_static {
     name: "libmodpb64",
     host_supported: true,
+    recovery_available: true,
     vendor_available: true,
     srcs: ["modp_b64.cc"],