cc/gcc: disable complibs if not selected

Force gcc to not link with some companion libraries when
there are not needed (because selected-out).

There is no option to tell gcc *not* to build the Graphite and/or
LTO stuff. They *will* be built if gcc finds the suitable companion
libraries. If we do not provide them, but the host has them, then
gcc *will* find them, and link with them.

Consider the following:
- host has suitable PPL and CLooG (eg. Debian Squeeze)
- user wants to build gcc>=4.4
- user de-selects GRAPHITE
- gcc will find the hosts PPL and CLooG, and will use them
- the user moves the toolchain to an older host that does
not have them (eg. Debian Lenny)
- the toolchain fails, when it was properly setup not to

So, explicitly tell gcc *not* to use unneeded companion libs.

Signed-off-by: "Yann E. MORIN" <yann.morin.1998@anciens.enib.fr>

 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)