Skip ld --gc-sections tests for MinGW

[Nick Clifton]

Hi Joseph,

> 2009-02-06  Joseph Myers  <joseph@codesourcery.com>
> 
> 	* lib/ld-lib.exp (check_gc_sections_available): Return 0 for
> 	*-*-mingw*.

Approved - please apply.

Cheers
   Nick