Update command to build docker to run in EKS cluster (#1648)

because with the previous command unable to get the argument.

Issue: #1647

Co-authored-by: za <za@noreply.users.github.com>

docs/running.md

@@ -92,7 +92,7 @@ aws ecr create-repository --repository-name k8s/kube-bench --image-tag-mutabilit
 git clone https://github.com/aquasecurity/kube-bench.git
 cd kube-bench
 aws ecr get-login-password --region <AWS_REGION> | docker login --username AWS --password-stdin <AWS_ACCT_NUMBER>.dkr.ecr.<AWS_REGION>.amazonaws.com
-docker build -t k8s/kube-bench .
+make build-docker IMAGE_NAME=k8s/kube-bench
 docker tag k8s/kube-bench:latest <AWS_ACCT_NUMBER>.dkr.ecr.<AWS_REGION>.amazonaws.com/k8s/kube-bench:latest
 docker push <AWS_ACCT_NUMBER>.dkr.ecr.<AWS_REGION>.amazonaws.com/k8s/kube-bench:latest
 ```