Update building-docker-images.md

Add missing explanation for DLC

Author: kimh

jekyll/_cci2/building-docker-images.md

@@ -103,8 +103,8 @@ jobs:
 Let’s break down what’s happening during this build’s execution:
 
 1. All commands are executed in the [primary container][primary-container].
-2. Once `setup_remote_docker` is called, a new remote environment is created, and your primary container is configured to use it.
-3. All docker-related commands are also executed in your primary container, but building/pushing images and running containers happens in the remote Docker Engine.
+2. Once `setup_remote_docker` is called, a new remote environment is created, and your primary container is configured to use it. All docker-related commands are also executed in your primary container, but building/pushing images and running containers happens in the remote Docker Engine.
+3. We enable [Docker Layer Caching](docker-layer-caching) here to speed up image building.
 4. We use project environment variables to store credentials for Docker Hub.
 
 ## Docker Version