Added section about useBuildCache

public-site/docs/src/references/reference-radix-config/index.md

@@ -42,6 +42,7 @@ spec:
 spec:
   build:
     useBuildKit: true
+    useBuildCache: true
     secrets:
       - SECRET_1
       - SECRET_2
@@ -63,6 +64,13 @@ Otherwise, there will be an error during the docker image build:
 Example: instead of `FROM alpine` use `FROM docker.io/alpine`, as this `alpine` image is located in the [Docker Hub](https://hub.docker.com/) repository.
 :::
 
+### `useBuildCache`
+`useBuildCache` - (optional, defaults to `true`) pushes all layers to cache, and uses it in future builds when possible. Requires `useBuildKit` to be enabled. Internally we set `--cache-to`, `--cache-from` and `--layers` in Buildah. Read more at [Buildahs Documentation](https://github.com/containers/buildah/blob/main/docs/buildah-build.1.md)
+
+:::tip SECURITY
+Currently all build jobs have access to all cached layers. Make sure you never store secrets or confidential information in any intermitent layer, multistage image, or in your final container image.
+:::
+
 ### `secrets`
 `secrets` - (optional) add secrets to Radix config `radixconfig.yaml` in the branch defined as `Config Branch` for your application. This will trigger a new build. This build will fail as no specified build secret has been set. You will now be able to set the secret **values** in the configuration section of your app in the Radix Web Console. These secrets also can be used in the [sub-pipelines](../../guides/sub-pipeline).