Merge branch 'docs-amend-autodeploy-ec2' into 'master'

Add prerequisites for autodeploy to ec2

See merge request gitlab-org/gitlab!47371

doc/ci/cloud_deployment/index.md

@@ -284,11 +284,14 @@ When running your project pipeline at this point:
 
 #### Custom build job for Auto DevOps
 
+> [Introduced](https://gitlab.com/gitlab-org/gitlab/-/issues/216008) in GitLab 13.6.
+
 To leverage [Auto DevOps](../../topics/autodevops/index.md) for your project when deploying to
-AWS EC2, you must specify a job for the `build` stage.
+AWS EC2, first you must define [your AWS credentials as environment variables](#run-aws-commands-from-gitlab-cicd).
 
-To do so, you must reference the `Auto-DevOps.gitlab-ci.yml` template and include a job named
-`build_artifact` in your `.gitlab-ci.yml` file. For example:
+Next, define a job for the `build` stage. To do so, you must reference the
+`Auto-DevOps.gitlab-ci.yml` template and include a job named `build_artifact` in your
+`.gitlab-ci.yml` file. For example:
 
 ```yaml
 # .gitlab-ci.yml