Reorder chunks in link.c so that the correct configuration is selected when
compiling with --with-gnu-ld on AIX.
No change in behaviour.

Note that in particular it's important that we use native AIX switches even
when using GNU ld.  This is important with response files as they must be
interpreted by collect2.

2011-10-16  Tristan Gingold  <gingold@adacore.com>

	* link.c (_AIX): Add support for GNU ld.