vendor: add buildkit

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

vendor/github.com/opencontainers/runc/libcontainer/system/unsupported.go

@@ -2,8 +2,26 @@
 
 package system
 
+import (
+	"os"
+
+	"github.com/opencontainers/runc/libcontainer/user"
+)
+
 // RunningInUserNS is a stub for non-Linux systems
 // Always returns false
 func RunningInUserNS() bool {
 	return false
 }
+
+// UIDMapInUserNS is a stub for non-Linux systems
+// Always returns false
+func UIDMapInUserNS(uidmap []user.IDMap) bool {
+	return false
+}
+
+// GetParentNSeuid returns the euid within the parent user namespace
+// Always returns os.Geteuid on non-linux
+func GetParentNSeuid() int {
+	return os.Geteuid()
+}