vendor: update buildkit to v0.19.0-rc1

Signed-off-by: Tonis Tiigi <tonistiigi@gmail.com>

vendor/github.com/containerd/errdefs/pkg/internal/cause/cause.go

@@ -0,0 +1,33 @@
+/*
+   Copyright The containerd Authors.
+
+   Licensed under the Apache License, Version 2.0 (the "License");
+   you may not use this file except in compliance with the License.
+   You may obtain a copy of the License at
+
+       http://www.apache.org/licenses/LICENSE-2.0
+
+   Unless required by applicable law or agreed to in writing, software
+   distributed under the License is distributed on an "AS IS" BASIS,
+   WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+   See the License for the specific language governing permissions and
+   limitations under the License.
+*/
+
+// Package cause is used to define root causes for errors
+// common to errors packages like grpc and http.
+package cause
+
+import "fmt"
+
+type ErrUnexpectedStatus struct {
+	Status int
+}
+
+const UnexpectedStatusPrefix = "unexpected status "
+
+func (e ErrUnexpectedStatus) Error() string {
+	return fmt.Sprintf("%s%d", UnexpectedStatusPrefix, e.Status)
+}
+
+func (ErrUnexpectedStatus) Unknown() {}