binutils: split binutils to backend/frontend, a-la cc_core

Move the actual binutils code to a backend function that builds the
required combo of build/host/target as requested by a frontend.

This split is currently a no-op, but is required for the upcoming
canadian-cross rework, where we'll be needing to build two binutils,
one for build/build/target, and one for build/host/target.

This applies to the three binutils:
- GNU binutils
- elf2flt
- sstrip

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

diff -durN gcc-3.4.6.orig/gcc/config/sh/sh.h gcc-3.4.6/gcc/config/sh/sh.h

--- gcc-3.4.6.orig/gcc/config/sh/sh.h	2006-01-12 02:20:32.000000000 +0100

+++ gcc-3.4.6/gcc/config/sh/sh.h	2007-08-15 23:03:09.000000000 +0200

@@ -422,6 +422,10 @@

 do {									\

   if (LEVEL)								\

     flag_omit_frame_pointer = -1;					\

+  if (LEVEL <= 2)							\

+    {									\

+      flag_reorder_blocks = 0;						\

+    }									\

   if (SIZE)								\

     target_flags |= SPACE_BIT;						\

   if (TARGET_SHMEDIA && LEVEL > 1)					\