Make scripts/update_payload available for other python modules

The new merge_ota tool will need this module to read/write OTA packages

Test: th
Bug: 227848550

Change-Id: Ibfe2fca65ffbaca939ea3f8ca924c9152e5e7540
diff --git a/Android.bp b/Android.bp
index 15c9ad3..9295985 100644
--- a/Android.bp
+++ b/Android.bp
@@ -162,6 +162,14 @@
     },
 }
 
+python_library_host {
+    name: "update_metadata-protos-python",
+    srcs: ["update_metadata.proto"],
+    proto: {
+        canonical_path_from_root: false,
+    },
+}
+
 // libpayload_consumer (type: static_library)
 // ========================================================
 // The payload application component and common dependencies.