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-4.5.2.orig/libjava/Makefile.in gcc-4.5.2/libjava/Makefile.in

 --- gcc-4.5.2.orig/libjava/Makefile.in	2010-12-16 13:49:03.000000000 +0100

 +++ gcc-4.5.2/libjava/Makefile.in	2010-12-29 23:02:41.000000000 +0100

 @@ -9463,6 +9463,9 @@

  ecjx$(EXEEXT): $(ecjx_OBJECTS) $(ecjx_DEPENDENCIES) 

  	@rm -f ecjx$(EXEEXT)

  	$(ecjx_LINK) $(ecjx_OBJECTS) $(ecjx_LDADD) $(LIBS)

 +ecjx.$(OBJEXT): $(ecjx_SOURCES)

 +	@rm -f ecjx.$(OBJEXT)

 +	$(CC_FOR_BUILD) $(BUILD_CFLAGS) -c -o $@ $<

  gappletviewer$(EXEEXT): $(gappletviewer_OBJECTS) $(gappletviewer_DEPENDENCIES) 

  	@rm -f gappletviewer$(EXEEXT)

  	$(gappletviewer_LINK) $(gappletviewer_OBJECTS) $(gappletviewer_LDADD) $(LIBS)