if err := os.Chmod(setgiddir, 0755|fs.ModeSetgid); err != nil {
		if testenv.SyscallIsNotSupported(err) {
			t.Skip("skipping: chmod is not supported on " + runtime.GOOS)
		}
		t.Fatal(err)
	}
	if fi, err := os.Stat(setgiddir); err != nil {
		t.Fatal(err)
	} else if fi.Mode()&fs.ModeSetgid == 0 {
		t.Skip("skipping: Chmod ignored ModeSetgid on " + runtime.GOOS)
	}

    private
    val fileAccessTracker by unsafeLazy {
        SingleDepthFileAccessTracker(fileAccessTimeJournal, cache.baseDir, cleanupDepth)
    }

    private
    fun chmod(file: File, mode: Int) {
        fileSystem.chmod(file, mode)
    }

    private
    fun markAccessed(stateFile: File) {
        fileAccessTracker.markAccessed(stateFile)
    }

    private