b := []byte(id)
	for _, p := range pos {
		if _, err := w.WriteAt(b, p); err != nil {
			return err
		}
	}

	// Update Mach-O code signature, if any.
	if f, cmd, ok := findMachoCodeSignature(w); ok {
		if codesign.Size(int64(cmd.Dataoff), "a.out") == int64(cmd.Datasize) {
			// Update the signature if the size matches, so we don't need to
			// fix up headers. Binaries generated by the Go linker should have