[Bug driver/91244] gcc-ar prepends --plugin option thus triggers binutils getopt_long bug 13256

[szotsaki at gmail dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=91244

--- Comment #1 from Szőts Ákos <szotsaki at gmail dot com> ---
Ps.: I've just realised that it's possible to unify the loop with the next
#else section and have only lines

  nargv[k + 0] = "--plugin";
  nargv[k + 1] = plugin;

inside the #if condition, thus removing code duplication.