chore(deps): bump github.com/moby/buildkit from 0.12.5 to 0.13.0 (#3072)

Bumps [github.com/moby/buildkit](https://github.com/moby/buildkit) from 0.12.5 to 0.13.0.
- [Release notes](https://github.com/moby/buildkit/releases)
- [Commits](https://github.com/moby/buildkit/compare/v0.12.5...v0.13.0)

---
updated-dependencies:
- dependency-name: github.com/moby/buildkit
  dependency-type: direct:production
  update-type: version-update:semver-minor
...

Signed-off-by: dependabot[bot] <support@github.com>
Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>

vendor/github.com/containerd/continuity/fs/dir.go

@@ -0,0 +1,53 @@
+/*
+   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 fs
+
+import (
+	"io"
+	"os"
+)
+
+type dirReader struct {
+	buf []os.DirEntry
+	f   *os.File
+	err error
+}
+
+func (r *dirReader) Next() os.DirEntry {
+	if len(r.buf) == 0 {
+		infos, err := r.f.ReadDir(32)
+		if err != nil {
+			if err != io.EOF {
+				r.err = err
+			}
+			return nil
+		}
+		r.buf = infos
+	}
+
+	if len(r.buf) == 0 {
+		return nil
+	}
+	out := r.buf[0]
+	r.buf[0] = nil
+	r.buf = r.buf[1:]
+	return out
+}
+
+func (r *dirReader) Err() error {
+	return r.err
+}