[PATCH] PR ld/20321: Warn and return for duplicated plugin

[Nick Clifton]

Hi H.J.

> 	PR ld/20321
> 	* plugin.c (plugin_opt_plugin): Warn and return if plugin has
> 	been loaded already.
> 	* testsuite/ld-plugin/lto.exp: Run PR ld/20321 test.
> 	* testsuite/ld-plugin/pr20321.c: New file.
 
Approved - please apply.

Cheers
  Nick