vendor: update buildkit to opentelemetry support

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

vendor/github.com/moby/buildkit/util/appcontext/appcontext.go

@@ -22,7 +22,12 @@ func Context() context.Context {
 		const exitLimit = 3
 		retries := 0
 
-		ctx, cancel := context.WithCancel(context.Background())
+		ctx := context.Background()
+		for _, f := range inits {
+			ctx = f(ctx)
+		}
+
+		ctx, cancel := context.WithCancel(ctx)
 		appContextCache = ctx
 
 		go func() {

vendor/github.com/moby/buildkit/util/appcontext/register.go

@@ -0,0 +1,14 @@
+package appcontext
+
+import (
+	"context"
+)
+
+type Initializer func(context.Context) context.Context
+
+var inits []Initializer
+
+// Register stores a new context initializer that runs on app context creation
+func Register(f Initializer) {
+	inits = append(inits, f)
+}