[Java11]Google Cloud BuildからGoogle Cloud Functionsにデプロイする

import com.google.cloud.functions.HttpFunction;
import com.google.cloud.functions.HttpRequest;
import com.google.cloud.functions.HttpResponse;

public class MessageFunction implements HttpFunction {
  @Override
  public void service(HttpRequest request, HttpResponse response) throws Exception {
    response.setContentType("Content-Type: text/plain; charset=UTF-8");

    if (request.getFirstQueryParameter("message").isEmpty()) {
      response.setStatusCode(400);
      response.getWriter().write("Query parameter 'message' is required");
      return;
    }

    String message = request.getFirstQueryParameter("message").get();
    if (message.length() == 0) {
      response.setStatusCode(400);
      response.getWriter().write("Query parameter 'message' is empty");
      return;
    }

    response.getWriter().write(message);
  }
}

steps:
  - name: 'gcr.io/cloud-builders/gcloud'
    args:
      - functions
      - deploy
      - Function名を指定する
      - --region=リージョンを指定
      - --source=.
      - --runtime=java11
      - --entry-point=HttpFunctionを実装したクラスをFQCNで指定
      - --trigger-http

ERROR: (gcloud.functions.deploy) OperationError: code=3, message=Build failed: Error: Could not find or load main class org.gradle.wrapper.GradleWrapperMain
Caused by: java.lang.ClassNotFoundException: org.gradle.wrapper.GradleWrapperMain; Error ID: 42fc8383
ERROR
ERROR: build step 0 "gcr.io/cloud-builders/gcloud" failed: step exited with non-zero status: 1

Step #1: Already have image (with digest): gcr.io/cloud-builders/gcloud
Step #1: Created .gcloudignore file. See `gcloud topic gcloudignore` for details.
Step #1: ERROR: (gcloud.functions.deploy) ResponseError: status=[403], code=[Forbidden], message=[Missing necessary permission iam.serviceAccounts.actAs for $MEMBER on the service account アカウント名.
Step #1: Ensure that service account アカウント名 is a member of the project プロジェクト名, and then grant $MEMBER the role 'roles/iam.serviceAccountUser'. 
Step #1: You can do that by running 'gcloud iam service-accounts add-iam-policy-binding アカウント名 --member=$MEMBER --role=roles/iam.serviceAccountUser' 
Step #1: In case the member is a service account please use the prefix 'serviceAccount:' instead of 'user:'. Please visit https://cloud.google.com/functions/docs/troubleshooting for in-depth troubleshooting documentation.]
Finished Step #1
ERROR
ERROR: build step 1 "gcr.io/cloud-builders/gcloud" failed: step exited with non-zero status: 1

Error: Forbidden
Your client does not have permission to get URL /xxxxx from this server.

tasks.withType(JavaCompile) {
    options.encoding = 'UTF-8'
}