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 -dur strace-4.5.15.orig/configure.ac strace-4.5.15/configure.ac

--- strace-4.5.15.orig/configure.ac	2007-07-14 19:25:25.000000000 +0200

+++ strace-4.5.15/configure.ac	2007-07-14 19:27:35.000000000 +0200

@@ -91,14 +91,14 @@

 	arch=hppa

 	AC_DEFINE([HPPA], 1, [Define for the HPPA architecture.])

 	;;

-sh)

-	arch=sh

-	AC_DEFINE([SH], 1, [Define for the SH architecture.])

-	;;

 sh64)

 	arch=sh64

 	AC_DEFINE([SH64], 1, [Define for the SH64 architecture.])

 	;;

+sh*)

+	arch=sh

+	AC_DEFINE([SH], 1, [Define for the SH architecture.])

+	;;

 x86?64*)

 	arch=x86_64

 	AC_DEFINE([X86_64], 1, [Define for the AMD x86-64 architecture.])