docs: reference buildx as a requirement for docker builds

Signed-off-by: Christopher M. Luciano <cmluciano@us.ibm.com>

Makefile

@@ -272,7 +272,7 @@ check-go-version:
 init-docker-buildx:
 ifeq ($(DIND_TASKS),)
 ifneq ($(shell docker buildx 2>&1 >/dev/null; echo $?),)
-	$(error "buildx not vailable. Docker 19.03 or higher is required")
+	$(error "buildx not available. Docker 19.03 or higher is required with experimental features enabled")
 endif
 	docker run --rm --privileged docker/binfmt:66f9012c56a8316f9244ffd7622d7c21c1f6f28d
 	docker buildx create --name ingress-nginx --use || true

docs/development.md

@@ -19,6 +19,8 @@ cd ingress-nginx
 
 ### Initial developer environment build
 
+Ensure docker experimental features option is enabled for [buildx](https://docs.docker.com/buildx/working-with-buildx/)
+
 ```
 $ make dev-env
 ```