Add protobuf definition for lz4diff

We develope a new diffing format, called lz4diff. Since this diff format
need to store per-block compression information(which algorithm is used,
compressed size, etc), a new protobuf message is added to ease
development.

Test: th
Bug: 206729162

Change-Id: Ib05e865a6689f561cd00b28843c98d52d0714869
diff --git a/Android.bp b/Android.bp
index ac94229..19026ac 100644
--- a/Android.bp
+++ b/Android.bp
@@ -953,3 +953,20 @@
         "update_metadata-protos",
     ],
 }
+
+cc_library_static {
+    name: "lz4diff-protos",
+    host_supported: true,
+    ramdisk_available: true,
+    recovery_available: true,
+
+    srcs: ["lz4diff/lz4diff.proto"],
+    cflags: [
+        "-Wall",
+        "-Werror",
+    ],
+    proto: {
+        canonical_path_from_root: false,
+        export_proto_headers: true,
+    },
+}