vendor: update buildkit to opentelemetry support

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

vendor/github.com/cenkalti/backoff/v4/context.go

@@ -0,0 +1,62 @@
+package backoff
+
+import (
+	"context"
+	"time"
+)
+
+// BackOffContext is a backoff policy that stops retrying after the context
+// is canceled.
+type BackOffContext interface { // nolint: golint
+	BackOff
+	Context() context.Context
+}
+
+type backOffContext struct {
+	BackOff
+	ctx context.Context
+}
+
+// WithContext returns a BackOffContext with context ctx
+//
+// ctx must not be nil
+func WithContext(b BackOff, ctx context.Context) BackOffContext { // nolint: golint
+	if ctx == nil {
+		panic("nil context")
+	}
+
+	if b, ok := b.(*backOffContext); ok {
+		return &backOffContext{
+			BackOff: b.BackOff,
+			ctx:     ctx,
+		}
+	}
+
+	return &backOffContext{
+		BackOff: b,
+		ctx:     ctx,
+	}
+}
+
+func getContext(b BackOff) context.Context {
+	if cb, ok := b.(BackOffContext); ok {
+		return cb.Context()
+	}
+	if tb, ok := b.(*backOffTries); ok {
+		return getContext(tb.delegate)
+	}
+	return context.Background()
+}
+
+func (b *backOffContext) Context() context.Context {
+	return b.ctx
+}
+
+func (b *backOffContext) NextBackOff() time.Duration {
+	select {
+	case <-b.ctx.Done():
+		return Stop
+	default:
+		return b.BackOff.NextBackOff()
+	}
+}