Create a new task that creates a diff zip with maven.google

This CL adds a new task (createDiffArchive) that includes the
zip of all artifacts that are not already on maven.google.com.

This is necessary because the upload script rejects the bundle
if it includes any libraries that are already public.

Test: manual
Bug: 66236485
Change-Id: I74c680449034bb3252d9f74305554af13e3c32c5
diff --git a/app-toolkit/init.gradle b/app-toolkit/init.gradle
index 8f60355..cd56153 100644
--- a/app-toolkit/init.gradle
+++ b/app-toolkit/init.gradle
@@ -89,7 +89,7 @@
 
 buildServerAnchorTask.dependsOn zipFlatfootDocsTask
 zipFlatfootDocsTask.dependsOn rootProject.tasks["generateDocs"]
-
+buildServerAnchorTask.dependsOn createDiffArchive
 buildServerAnchorTask.dependsOn createArchive
 
 rootProject.ext.flatfootProjectGroups = [