code: func runExec(bin string, args []string, e *env) error {
  	if sysExec != nil {
  		sysExec(bin, append([]string{filepath.Base(bin)}, args...), e.flat())
  	}
  
  	cmd := exec.Command(bin, args...)
  	cmd.Env = e.flat()
  	cmd.Stdout = Stdout
  	cmd.Stderr = Stderr
  	return cmd.Run()
  }
docs: // runExec execs bin. If the platform doesn't support exec, it runs it and waits
  // for it to finish.