Add configurable multi-arch build support

Signed-off-by: Catherine Chan-Tse <[email protected]>

Author: oceanc80

Diff for: docs/tutorial.md

@@ -87,7 +87,7 @@ The `java-operator-plugins` project uses the APIs from [java-operator-sdk](https
 
 #### `MemcachedSpec`
 
-Initially, the scaffolded Spec file will be empty. The operator developer needs
+Initially, the scaffolded Spec file, `MemcachedSpec`, will be empty. The operator developer needs
 to add attributes to this file according to their needs. For the `Memcached`
 example, we will add the size field as shown in the example below.
 
@@ -564,15 +564,20 @@ The following steps will show how to run your operator in the cluster.
 
 The `java-operator-plugins` project will scaffold out a Makefile to give
 Operator SDK users a familiar interface. Using the `docker-*` targets you can
-conveniently build your and push your operator's image to registry. In our
-example, we are using `quay.io`, but any docker registry should work.
+conveniently build and push your operator's image to a registry.
+
+To build and push the docker image, you will need to specify the name of the image, `IMG`,
+that will be built as well as the operating system, `OS`, and the architecture,
+`ARCH`, that the image will be built for. In this example, we are using
+`quay.io` as the registry the image will be pushed to, but any docker registry should work.
 
 ```
-make docker-build docker-push IMG=quay.io/YOURUSER/memcached-quarkus-operator:v0.0.1
+make docker-build docker-push IMG=quay.io/YOURUSER/memcached-quarkus-operator:v0.0.1 OS=linux ARCH=arm64
 ```
 
-This will build the docker image
-`quay.io/YOURUSER/memcached-quarkus-operator:v0.0.1` and push it to the registry.
+This will build the docker image 
+`quay.io/YOURUSER/memcached-quarkus-operator:v0.0.1` for linux/arm64 and push it
+to the `quay.io` registry.
 
 You can verify it is in your docker registry:
 

Diff for: pkg/quarkus/v1alpha/scaffolds/internal/templates/makefile.go

@@ -62,8 +62,11 @@ func (f *Makefile) SetTemplateDefaults() error {
 }
 
 const makefileTemplate = `
-# Image URL to use all building/pushing image targets
+# Image URL to use for all building/pushing image targets
 IMG ?= {{ .Image }}
+# Operating system and architecture to use for building image
+OS ?= {{ .OS }}
+ARCH ?= {{ .Arch }}
 
 all: docker-build
 
@@ -86,7 +89,7 @@ help: ## Display this help.
 ##@ Build
 
 docker-build: ## Build docker image with the manager.
-	mvn package -Dquarkus.container-image.build=true -Dquarkus.container-image.image=${IMG}
+	mvn package -Dquarkus.container-image.build=true -Dquarkus.container-image.builder=docker -Dquarkus.container-image.image=${IMG} -Dquarkus.docker.buildx.platform=${OS}/${ARCH}
 
 docker-push: ## Push docker image with the manager.
 	mvn package -Dquarkus.container-image.push=true -Dquarkus.container-image.image=${IMG}