Upload gradle binary to GCS when preparing the release

This makes it possible to pull the gradle binary from a trusted source when building the release artifacts.

-------------
Created by MOE: https://github.com/google/moe
MOE_MIGRATED_REVID=245450562

release/cloudbuild-release.yaml

@@ -38,7 +38,7 @@ steps:
     rm -rf .git && rm -rf nomulus-internal/.git
     cp -rf nomulus-internal/* .
     rm -rf nomulus-internal
-# Build the builder image and tag the proxy base image, to be uploaded later.
+# Build the builder image and tag the proxy base image, then upload them to GCR.
 - name: 'gcr.io/cloud-builders/docker'
   entrypoint: /bin/bash
   args:
@@ -68,6 +68,32 @@ steps:
     sed -i s/builder:latest/builder@$builder_digest/g release/cloudbuild-proxy.yaml
     sed -i s/builder:latest/builder@$builder_digest/g release/cloudbuild-nomulus.yaml
     sed -i s/GCP_PROJECT/${PROJECT_ID}/ java/google/registry/proxy/kubernetes/proxy-*.yaml
+# Upload the gradle binary to GCS if it does not exist and point URL in gradle wrapper to it.
+- name: 'gcr.io/cloud-builders/gsutil'
+  entrypoint: /bin/bash
+  args:
+  - -c
+  - |
+    gradle_url=$(grep distributionUrl gradle/gradle/wrapper/gradle-wrapper.properties \
+      | awk -F = '{print $2}' | sed 's/\\//g')
+    gradle_bin=$(basename $gradle_url)
+    gcs_loc="domain-registry-maven-repository/gradle"
+    curl -O -L ${gradle_url}
+    if gsutil -q stat gs://${gcs_loc}/${gradle_bin}
+    then
+      local_md5=$(md5sum ${gradle_bin} | awk '{print $1}')
+      remote_md5=$(gsutil hash -h gs://${gcs_loc}/${gradle_bin} | grep md5 | awk '{print $3}')
+      if [[ ${local_md5} != ${remote_md5} ]]
+      then
+        echo "${gradle_bin} HAS CHANGED ON GRADLE WEBSITE, USING THE BINARY ON GCS."
+      fi
+    else
+      gsutil cp $gradle_bin gs://${gcs_loc}/
+      gsutil acl ch -u AllUsers:R gs://${gcs_loc}/${gradle_bin}
+    fi
+    rm ${gradle_bin}
+    sed -i s%services.gradle.org/distributions%storage.googleapis.com/${gcs_loc}% \
+      gradle/gradle/wrapper/gradle-wrapper.properties
 # Check out the release repo.
 - name: 'gcr.io/cloud-builders/gcloud'
   args: ['source', 'repos', 'clone', 'nomulus-release']