vendor: update buildkit to v0.18.0-rc1

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

vendor/github.com/tonistiigi/fsutil/copy/copy_otherbsd.go

@@ -0,0 +1,38 @@
+//go:build openbsd || netbsd
+// +build openbsd netbsd
+
+package fs
+
+import (
+	"io"
+	"os"
+
+	"github.com/pkg/errors"
+	"golang.org/x/sys/unix"
+)
+
+func copyFile(source, target string) error {
+	src, err := os.Open(source)
+	if err != nil {
+		return errors.Wrapf(err, "failed to open source %s", source)
+	}
+	defer src.Close()
+	tgt, err := os.Create(target)
+	if err != nil {
+		return errors.Wrapf(err, "failed to open target %s", target)
+	}
+	defer tgt.Close()
+
+	return copyFileContent(tgt, src)
+}
+
+func copyFileContent(dst, src *os.File) error {
+	buf := bufferPool.Get().(*[]byte)
+	_, err := io.CopyBuffer(dst, src, *buf)
+	bufferPool.Put(buf)
+	return err
+}
+
+func mknod(dst string, mode uint32, rDev int) error {
+	return unix.Mknod(dst, uint32(mode), rDev)
+}