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/syscall.c strace-4.5.15/syscall.c

 --- strace-4.5.15.orig/syscall.c	2007-07-14 19:21:44.000000000 +0200

 +++ strace-4.5.15/syscall.c	2007-07-14 19:22:49.000000000 +0200

 @@ -125,6 +125,18 @@

  #define TP TRACE_PROCESS

  #define TS TRACE_SIGNAL

 +#ifndef HAVE_STATFS64

 +/*

 + * Ugly hacks for systems that do not have LFS

 + */

 +

 +#define sys_truncate64  sys_truncate

 +#define sys_ftruncate64 sys_ftruncate

 +#define sys_getdents64  sys_getdents

 +#define sys_statfs64    sys_statfs

 +#define sys_fstatfs64   sys_fstatfs

 +#endif

 +

  static const struct sysent sysent0[] = {

  #include "syscallent.h"

  };