archive: disable looking up usernames and groupnames on the host

These strings were resolved using the user information on the host
filesystem and were decreasing reproducibility.

For moby/buildkit issue 3688

Signed-off-by: Akihiro Suda <akihiro.suda.cz@hco.ntt.co.jp>

archive/tarheader/tarheader_unix.go

@@ -0,0 +1,59 @@
+//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.
+*/
+
+/*
+   Portions from https://github.com/moby/moby/blob/v23.0.1/pkg/archive/archive_unix.go#L52-L70
+   Copyright (C) Docker/Moby authors.
+   Licensed under the Apache License, Version 2.0
+   NOTICE: https://github.com/moby/moby/blob/v23.0.1/NOTICE
+*/
+
+package tarheader
+
+import (
+	"archive/tar"
+	"os"
+	"syscall"
+
+	"golang.org/x/sys/unix"
+)
+
+func init() {
+	sysStat = statUnix
+}
+
+// statUnix populates hdr from system-dependent fields of fi without performing
+// any OS lookups.
+// From https://github.com/moby/moby/blob/v23.0.1/pkg/archive/archive_unix.go#L52-L70
+func statUnix(fi os.FileInfo, hdr *tar.Header) error {
+	s, ok := fi.Sys().(*syscall.Stat_t)
+	if !ok {
+		return nil
+	}
+
+	hdr.Uid = int(s.Uid)
+	hdr.Gid = int(s.Gid)
+
+	if s.Mode&unix.S_IFBLK != 0 ||
+		s.Mode&unix.S_IFCHR != 0 {
+		hdr.Devmajor = int64(unix.Major(uint64(s.Rdev)))
+		hdr.Devminor = int64(unix.Minor(uint64(s.Rdev)))
+	}
+
+	return nil
+}