llbsolver: set temporary lease in Commit context

The temporary lease must be passed via the context for the call to
w.Commit() to prevent the cleanup of metadata resources before they are
fully referenced.

This fixes moby#3921

Signed-off-by: Alex Couture-Beil <[email protected]>

Author: Alex Couture-Beil

solver/llbsolver/history.go

@@ -579,7 +579,7 @@ func (w *Writer) Discard() {
 func (w *Writer) Commit(ctx context.Context) (*ocispecs.Descriptor, func(), error) {
 	dgst := w.dgstr.Digest()
 	sz := int64(w.sz)
-	if err := w.w.Commit(ctx, int64(w.sz), dgst); err != nil {
+	if err := w.w.Commit(leases.WithLease(ctx, w.l.ID), int64(w.sz), dgst); err != nil {
 		if !errdefs.IsAlreadyExists(err) {
 			w.Discard()
 			return nil, nil, err