binutils/binutils: simplify gold dependencies

In preparation of adding a new kernel-type, Yann D. came up
with a change in semantic on binutils/gold availability.

So far, it was architectures' responsibility to declare that
they did support binutils/gold or not. It makes much more sense
that binutils/gold declares its own availability depending on
the current architecture; after all, architectures have no way
to know wether gold supports them, while gold does know it.

Signed-off-by:Yann Diorcet <diorcet.yann@gmail.com>
[yann.morin.1998@free.fr: split up original patch for self-contained changes]
Signed-off-by: "Yann E. MORIN" <yann.morin.1998@free.fr>
Message-Id: <d3d1d51f399e6d2c1163.1353320546@macbook-smorlat.local>
Patchwork-Id: 199971

 diff -dur binutils-2.17.old/bfd/opncls.c binutils-2.17/bfd/opncls.c

 --- binutils-2.17.old/bfd/opncls.c	2006-03-16 13:20:16.000000000 +0100

 +++ binutils-2.17/bfd/opncls.c	2007-05-01 18:26:11.000000000 +0200

 @@ -158,6 +158,13 @@

  {

    bfd *nbfd;

    const bfd_target *target_vec;

 +  struct stat s;

 +

 +  if (stat (filename, &s) == 0)

 +    if (S_ISDIR(s.st_mode)) {

 +      bfd_set_error (bfd_error_file_not_recognized);

 +      return NULL;

 +    }

    nbfd = _bfd_new_bfd ();

    if (nbfd == NULL)