Fleshed out the framework of most of the wwctl overlay command group.

internal/app/wwctl/overlay/build/root.go

@@ -0,0 +1,25 @@
+package build
+
+import "github.com/spf13/cobra"
+
+var (
+	baseCmd = &cobra.Command{
+		Use:                "build [overlay name]",
+		Short:              "Build/Rebuild an overlay",
+		Long:               "Build or rebuild a Warewulf overlay ",
+		RunE:				CobraRunE,
+	}
+	SystemOverlay bool
+	BuildAll bool
+)
+
+func init() {
+	baseCmd.PersistentFlags().BoolVarP(&SystemOverlay, "system", "s", false, "Show System Overlays as well")
+	baseCmd.PersistentFlags().BoolVarP(&BuildAll, "all", "a", false, "Build all overlays (runtime and system)")
+
+}
+
+// GetRootCommand returns the root cobra.Command for the application.
+func GetCommand() *cobra.Command {
+	return baseCmd
+}