ctr: Add sandbox flag to ctr run

Add a flag to be able to run a container in a given sandbox.

Signed-off-by: Danny Canter <danny@dcantah.dev>

cmd/ctr/commands/run/run_unix.go

@@ -102,6 +102,10 @@ func NewContainer(ctx gocontext.Context, client *containerd.Client, context *cli
 		spec  containerd.NewContainerOpts
 	)
 
+	if sandbox := context.String("sandbox"); sandbox != "" {
+		cOpts = append(cOpts, containerd.WithSandbox(sandbox))
+	}
+
 	if config {
 		cOpts = append(cOpts, containerd.WithContainerLabels(commands.LabelArgs(context.StringSlice("label"))))
 		opts = append(opts, oci.WithSpecFromFile(context.String("config")))