code: func runExec(bin string, args []string, env *Env) error {
  	if sysExec != nil {
  		sysExec(bin, append([]string{filepath.Base(bin)}, args...), env.Flat())
  	}
  
  	cmd := exec.Command(bin, args...)
  	cmd.Env = env.Flat()
  	cmd.Stdout = os.Stdout
  	cmd.Stderr = os.Stderr
  	if err := cmd.Start(); err != nil {
  		return fmt.Errorf("Could not run %v: %v", bin, err)
  	}
  	go handleSignals(cmd.Process)
  	return cmd.Wait()
  }
docs: // runExec execs bin. If the platform doesn't support exec, it runs it and waits
  // for it to finish.