Fix PR12762 using linkonce sections in plugin bfd

[Alan Modra]

On Thu, Aug 11, 2011 at 08:07:43AM -0700, H.J. Lu wrote:
> FAIL: PR ld/12942 (1)

Sigh.  Yes, we do need to set up the already_linked list on the first
pass for lto objects.  It wasn't working simply because the linkonce
attribute doesn't make it through bfd_make_readable().  I have a patch
that works on the testcase, but I'll do a gcc bootstrap and regression
test before inflicting it on you.

-- 
Alan Modra
Australia Development Lab, IBM