vendor: add buildkit

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

vendor/github.com/moby/buildkit/util/appdefaults/appdefaults_windows.go

@@ -0,0 +1,23 @@
+package appdefaults
+
+const (
+	Address   = "npipe:////./pipe/buildkitd"
+	Root      = ".buildstate"
+	ConfigDir = ""
+)
+
+func UserAddress() string {
+	return Address
+}
+
+func EnsureUserAddressDir() error {
+	return nil
+}
+
+func UserRoot() string {
+	return Root
+}
+
+func UserConfigDir() string {
+	return ConfigDir
+}