distro/rhel9: update tar image type to new definition

Add the image function and remove the pipeline function.
Remove the build package set.

internal/distro/rhel9/bare_metal.go

@@ -13,7 +13,6 @@ var (
 		filename: "root.tar.xz",
 		mimeType: "application/x-tar",
 		packageSets: map[string]packageSetFunc{
-			buildPkgsKey: distroBuildPackageSet,
 			osPkgsKey: func(t *imageType) rpmmd.PackageSet {
 				return rpmmd.PackageSet{
 					Include: []string{"policycoreutils", "selinux-policy-targeted"},
@@ -24,7 +23,7 @@ var (
 		packageSetChains: map[string][]string{
 			osPkgsKey: {osPkgsKey, blueprintPkgsKey},
 		},
-		pipelines:        tarPipelines,
+		image:            tarImage,
 		buildPipelines:   []string{"build"},
 		payloadPipelines: []string{"os", "root-tar"},
 		exports:          []string{"root-tar"},

internal/distro/rhel9/images.go

@@ -354,3 +354,23 @@ func imageInstallerImage(workload workload.Workload,
 
 	return img, nil
 }
+
+func tarImage(workload workload.Workload,
+	t *imageType,
+	customizations *blueprint.Customizations,
+	options distro.ImageOptions,
+	packageSets map[string]rpmmd.PackageSet,
+	containers []container.Spec,
+	rng *rand.Rand) (image.ImageKind, error) {
+
+	img := image.NewArchive()
+	img.Platform = t.platform
+	img.OSCustomizations = osCustomizations(t, packageSets[osPkgsKey], options, containers, customizations)
+	img.Environment = t.environment
+	img.Workload = workload
+
+	img.Filename = t.Filename()
+
+	return img, nil
+
+}