distro: add Distro.Name()

Right now, there is no way to get at the name from a Distro instance.
We will need this to include the distro's name in the job we pass to the
worker, for instance.

internal/distro/rhel82/distro.go

@@ -38,6 +38,8 @@ type output struct {
 	Assembler        func(uefi bool) *pipeline.Assembler
 }
 
+const Name = "rhel-8.2"
+
 func New() *RHEL82 {
 	const GigaByte = 1024 * 1024 * 1024
 
@@ -392,6 +394,10 @@ func New() *RHEL82 {
 	return &r
 }
 
+func (r *RHEL82) Name() string {
+	return Name
+}
+
 func (r *RHEL82) Repositories(arch string) []rpmmd.RepoConfig {
 	return []rpmmd.RepoConfig{
 		{