vendor: update buildkit

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

vendor/github.com/moby/buildkit/client/connhelper/connhelper.go

@@ -0,0 +1,37 @@
+// Package connhelper provides helpers for connecting to a remote daemon host with custom logic.
+package connhelper
+
+import (
+	"context"
+	"net"
+	"net/url"
+
+	"github.com/docker/cli/cli/connhelper/commandconn"
+)
+
+// ConnectionHelper allows to connect to a remote host with custom stream provider binary.
+type ConnectionHelper struct {
+	// ContextDialer can be passed to grpc.WithContextDialer
+	ContextDialer func(ctx context.Context, addr string) (net.Conn, error)
+}
+
+// GetConnectionHelper returns BuildKit-specific connection helper for the given URL.
+// GetConnectionHelper returns nil without error when no helper is registered for the scheme.
+//
+// docker://<container> URL requires BuildKit v0.5.0 or later in the container.
+func GetConnectionHelper(daemonURL string) (*ConnectionHelper, error) {
+	u, err := url.Parse(daemonURL)
+	if err != nil {
+		return nil, err
+	}
+	switch scheme := u.Scheme; scheme {
+	case "docker":
+		container := u.Host
+		return &ConnectionHelper{
+			ContextDialer: func(ctx context.Context, addr string) (net.Conn, error) {
+				return commandconn.New(ctx, "docker", "exec", "-i", container, "buildctl", "dial-stdio")
+			},
+		}, nil
+	}
+	return nil, err
+}