go func() {
		var buf bytes.Buffer
		enc := json.NewEncoder(&buf)
		for {
			select {
			case <-ctx.Done():
				return
			case li := <-logCh:
				if !li.SendLog(node, logKind) {
					continue
				}
				buf.Reset()
				if err := enc.Encode(li); err != nil {
					continue
				}
				select {
				case <-ctx.Done():
					return

		if !strings.HasPrefix(arg, "-O") {
			nargs = append(nargs, arg)
		}
	}

	// Force -O0 optimization and append extra arguments, but keep the
	// trailing "-" at the end.
	li := len(nargs) - 1
	last := nargs[li]
	nargs[li] = "-O0"
	nargs = append(nargs, extraArgs...)
	nargs = append(nargs, last)

	if *debugGcc {
		fmt.Fprintf(os.Stderr, "$ %s <<EOF\n", strings.Join(nargs, " "))