vendor: update buildkit to v0.15.0-rc1

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

vendor/github.com/gofrs/flock/flock_others.go

@@ -0,0 +1,40 @@
+//go:build (!unix && !windows) || plan9
+
+package flock
+
+import (
+	"errors"
+	"io/fs"
+)
+
+func (f *Flock) Lock() error {
+	return &fs.PathError{
+		Op:   "Lock",
+		Path: f.Path(),
+		Err:  errors.ErrUnsupported,
+	}
+}
+
+func (f *Flock) RLock() error {
+	return &fs.PathError{
+		Op:   "RLock",
+		Path: f.Path(),
+		Err:  errors.ErrUnsupported,
+	}
+}
+
+func (f *Flock) Unlock() error {
+	return &fs.PathError{
+		Op:   "Unlock",
+		Path: f.Path(),
+		Err:  errors.ErrUnsupported,
+	}
+}
+
+func (f *Flock) TryLock() (bool, error) {
+	return false, f.Lock()
+}
+
+func (f *Flock) TryRLock() (bool, error) {
+	return false, f.RLock()
+}