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 glibc-2.12.1.orig/elf/dl-lookup.c glibc-2.12.1/elf/dl-lookup.c

--- glibc-2.12.1.orig/elf/dl-lookup.c	2009-03-30 23:14:32.000000000 +0200

+++ glibc-2.12.1/elf/dl-lookup.c	2009-11-13 00:51:36.000000000 +0100

@@ -301,6 +301,12 @@

 	      /* FALLTHROUGH */

 	    case STB_GLOBAL:

	    success:

+#ifdef __mips__

+	      /* HACK: MIPS marks its lazy evaluation stubs with SHN_UNDEF

+		 symbols, we skip them. */

+	      if (sym->st_shndx == SHN_UNDEF)

+		break;

+#endif

 	      /* Global definition.  Just what we need.  */

 	      result->s = sym;

 	      result->m = (struct link_map *) map;