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 gcc-4.4.4.orig/gcc/config.gcc gcc-4.4.4/gcc/config.gcc

 --- gcc-4.4.4.orig/gcc/config.gcc	2010-02-18 05:24:04.000000000 +0100

 +++ gcc-4.4.4/gcc/config.gcc	2010-05-16 19:13:30.000000000 +0200

 @@ -2128,7 +2128,7 @@

  	if test x${sh_multilibs} = x ; then

  		case ${target} in

  		sh64-superh-linux* | \

 -		sh[1234]*)	sh_multilibs=${sh_cpu_target} ;;

 +		sh[1234]*)	sh_multilibs=`cd ${srcdir}/config/sh ; echo t-mlib-sh[1-4]* | sed 's:t-mlib-sh:,m:g;s: ::g'` ;;

  		sh64* | sh5*)	sh_multilibs=m5-32media,m5-32media-nofpu,m5-compact,m5-compact-nofpu,m5-64media,m5-64media-nofpu ;;

  		sh-superh-*)	sh_multilibs=m4,m4-single,m4-single-only,m4-nofpu ;;

  		sh*-*-linux*)	sh_multilibs=m1,m3e,m4 ;;