cc/gcc: add the backend/frontend infra for final gcc

Currently, we issue the bare-metal compiler from the pass_1 & pass_2
core compilers, because the final gcc breaks while doing so.

This implies we have to build some libces during the start_files step,
instead of the standard libc step. This is the case for newlib.

By adding a backend/frontend infra to the final gcc, we can abstract
what backend to call: the standard backend for non-bare-metal gcc,
and the core backend for bare-metal.

This patch is just an no-op, it just adds the final backend and
frontend without changing the way bare-metal is built, to come in a
subsequent patch.

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

diff -durN binutils-2.20.1.orig/bfd/elf64-ppc.c binutils-2.20.1/bfd/elf64-ppc.c

--- binutils-2.20.1.orig/bfd/elf64-ppc.c	2010-02-03 14:28:25.000000000 +0100

+++ binutils-2.20.1/bfd/elf64-ppc.c	2010-08-17 19:32:04.000000000 +0200

@@ -11991,7 +11991,12 @@

 	      else if (!SYMBOL_REFERENCES_LOCAL (info, &h->elf)

 		       && !is_opd

 		       && r_type != R_PPC64_TOC)

-		outrel.r_info = ELF64_R_INFO (h->elf.dynindx, r_type);

+		{

+		  outrel.r_info = ELF64_R_INFO (h->elf.dynindx, r_type);

+		  if (h->elf.dynindx == -1

+		      && h->elf.root.type == bfd_link_hash_undefweak)

+		  memset (&outrel, 0, sizeof outrel);

+		}

 	      else

 		{

 		  /* This symbol is local, or marked to become local,