manifest: Add support for plain erofs root filesystem on the iso

Add support for erofs by setting the RootfsType on
AnacondaInstallerISOTree to ErofsRootfs to select a plain erofs
compressed root filesystem for the Anaconda ISO.

The mkfs.erofs arguments will look like this:
zstd,8 -E all-fragments,dedupe -C 131072

pkg/manifest/anaconda_installer_iso_tree.go

@@ -23,6 +23,7 @@ type RootfsType uint64
 const ( // Rootfs type enum
 	SquashfsExt4Rootfs RootfsType = iota // Create an EXT4 rootfs compressed by Squashfs
 	SquashfsRootfs                       // Create a plain squashfs rootfs
+	ErofsRootfs                          // Create a plain erofs rootfs
 )
 
 // An AnacondaInstallerISOTree represents a tree containing the anaconda installer,
@@ -136,8 +137,13 @@ func (p *AnacondaInstallerISOTree) getInline() []string {
 	return inlineData
 }
 func (p *AnacondaInstallerISOTree) getBuildPackages(_ Distro) []string {
-	packages := []string{
-		"squashfs-tools",
+	var packages []string
+	switch p.RootfsType {
+	case SquashfsExt4Rootfs, SquashfsRootfs:
+		packages = []string{"squashfs-tools"}
+	case ErofsRootfs:
+		packages = []string{"erofs-utils"}
+	default:
 	}
 
 	if p.OSTreeCommitSource != nil {
@@ -191,6 +197,36 @@ func (p *AnacondaInstallerISOTree) NewSquashfsStage() *osbuild.Stage {
 	return osbuild.NewSquashfsStage(&squashfsOptions, p.anacondaPipeline.Name())
 }
 
+// NewErofsStage returns an osbuild stage configured to build
+// the erofs root filesystem for the ISO.
+func (p *AnacondaInstallerISOTree) NewErofsStage() *osbuild.Stage {
+	var erofsOptions osbuild.ErofsStageOptions
+
+	if p.anacondaPipeline.Type == AnacondaInstallerTypePayload {
+		erofsOptions = osbuild.ErofsStageOptions{
+			Filename: "images/install.img",
+		}
+	} else if p.anacondaPipeline.Type == AnacondaInstallerTypeLive {
+		erofsOptions = osbuild.ErofsStageOptions{
+			Filename: "LiveOS/squashfs.img",
+		}
+	}
+
+	var compression osbuild.ErofsCompression
+	if p.RootfsCompression != "" {
+		compression.Method = p.RootfsCompression
+	} else {
+		// default to zstd if not specified
+		compression.Method = "zstd"
+	}
+	compression.Level = common.ToPtr(8)
+	erofsOptions.Compression = &compression
+	erofsOptions.ExtendedOptions = []string{"all-fragments", "dedupe"}
+	erofsOptions.ClusterSize = common.ToPtr(131072)
+
+	return osbuild.NewErofsStage(&erofsOptions, p.anacondaPipeline.Name())
+}
+
 func (p *AnacondaInstallerISOTree) serializeStart(_ []rpmmd.PackageSpec, containers []container.Spec, commits []ostree.CommitSpec, _ []rpmmd.RepoConfig) {
 	if p.ostreeCommitSpec != nil || p.containerSpec != nil {
 		panic("double call to serializeStart()")
@@ -297,7 +333,15 @@ func (p *AnacondaInstallerISOTree) serialize() osbuild.Pipeline {
 	copyStageInputs := osbuild.NewPipelineTreeInputs(inputName, p.anacondaPipeline.Name())
 	copyStage := osbuild.NewCopyStageSimple(copyStageOptions, copyStageInputs)
 	pipeline.AddStage(copyStage)
-	pipeline.AddStage(p.NewSquashfsStage())
+
+	// Add the selected roofs stage
+	switch p.RootfsType {
+	case SquashfsExt4Rootfs, SquashfsRootfs:
+		pipeline.AddStage(p.NewSquashfsStage())
+	case ErofsRootfs:
+		pipeline.AddStage(p.NewErofsStage())
+	default:
+	}
 
 	if p.ISOLinux {
 		isoLinuxOptions := &osbuild.ISOLinuxStageOptions{