vendor: update buildkit to master@b49a8873179b

Signed-off-by: Justin Chadwell <me@jedevc.com>

tests/workers/backend.go

@@ -1,10 +1,20 @@
 package workers
 
+import (
+	"os"
+	"strings"
+
+	"github.com/moby/buildkit/util/testutil/integration"
+)
+
 type backend struct {
-	builder string
-	context string
+	builder             string
+	context             string
+	unsupportedFeatures []string
 }
 
+var _ integration.Backend = &backend{}
+
 func (s *backend) Address() string {
 	return s.builder
 }
@@ -24,3 +34,26 @@ func (s *backend) Snapshotter() string {
 func (s *backend) Rootless() bool {
 	return false
 }
+
+func (b backend) Supports(feature string) bool {
+	if enabledFeatures := os.Getenv("BUILDKIT_TEST_ENABLE_FEATURES"); enabledFeatures != "" {
+		for _, enabledFeature := range strings.Split(enabledFeatures, ",") {
+			if feature == enabledFeature {
+				return true
+			}
+		}
+	}
+	if disabledFeatures := os.Getenv("BUILDKIT_TEST_DISABLE_FEATURES"); disabledFeatures != "" {
+		for _, disabledFeature := range strings.Split(disabledFeatures, ",") {
+			if feature == disabledFeature {
+				return false
+			}
+		}
+	}
+	for _, unsupportedFeature := range b.unsupportedFeatures {
+		if feature == unsupportedFeature {
+			return false
+		}
+	}
+	return true
+}