Document how to use AWS IAM profiles for object storage

[ci skip]

doc/administration/job_artifacts.md

@@ -116,6 +116,20 @@ _The artifacts are stored by default in
     }
     ```
 
+    NOTE: If you are using AWS IAM profiles, you will need to specify a blank
+    AWS access key and ID until [this fog-aws
+    issue](https://github.com/fog/fog-aws/issues/162) is resolved. For example:
+
+    ```ruby
+    gitlab_rails['artifacts_object_store_connection'] = {
+      'provider' => 'AWS',
+      'region' => 'eu-central-1',
+      'aws_access_key_id' => '',
+      'aws_secret_access_key' => '',
+      'use_iam_profile' => true
+    }
+    ```
+
 1. Save the file and [reconfigure GitLab][] for the changes to take effect.
 1. Migrate any existing local artifacts to the object storage: