vendor: update buildkit to v0.17.0-rc2

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

vendor/github.com/containerd/continuity/testutil/helpers_unix.go

@@ -0,0 +1,57 @@
+//go:build !windows
+
+/*
+   Copyright The containerd Authors.
+
+   Licensed under the Apache License, Version 2.0 (the "License");
+   you may not use this file except in compliance with the License.
+   You may obtain a copy of the License at
+
+       http://www.apache.org/licenses/LICENSE-2.0
+
+   Unless required by applicable law or agreed to in writing, software
+   distributed under the License is distributed on an "AS IS" BASIS,
+   WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+   See the License for the specific language governing permissions and
+   limitations under the License.
+*/
+
+package testutil
+
+import (
+	"os"
+	"testing"
+
+	"golang.org/x/sys/unix"
+)
+
+// Unmount unmounts a given mountPoint and sets t.Error if it fails
+func Unmount(t *testing.T, mountPoint string) {
+	t.Log("unmount", mountPoint)
+	if err := unmountAll(mountPoint); err != nil {
+		t.Error("Could not umount", mountPoint, err)
+	}
+}
+
+// RequiresRoot skips tests that require root, unless the test.root flag has
+// been set
+func RequiresRoot(t testing.TB) {
+	if !rootEnabled {
+		t.Skip("skipping test that requires root")
+		return
+	}
+	if os.Getuid() != 0 {
+		t.Error("This test must be run as root.")
+	}
+}
+
+func unmountAll(mountpoint string) error {
+	for {
+		if err := unix.Unmount(mountpoint, unmountFlags); err != nil {
+			if err == unix.EINVAL {
+				return nil
+			}
+			return err
+		}
+	}
+}