cc/gcc: disable complibs if not selected

Force gcc to not link with some companion libraries when
there are not needed (because selected-out).

There is no option to tell gcc *not* to build the Graphite and/or
LTO stuff. They *will* be built if gcc finds the suitable companion
libraries. If we do not provide them, but the host has them, then
gcc *will* find them, and link with them.

Consider the following:
- host has suitable PPL and CLooG (eg. Debian Squeeze)
- user wants to build gcc>=4.4
- user de-selects GRAPHITE
- gcc will find the hosts PPL and CLooG, and will use them
- the user moves the toolchain to an older host that does
not have them (eg. Debian Lenny)
- the toolchain fails, when it was properly setup not to

So, explicitly tell gcc *not* to use unneeded companion libs.

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

 --- gcc-4.1.2.orig/gcc/Makefile.in	2006-11-01 15:40:44.000000000 +0100

 +++ gcc-4.1.2/gcc/Makefile.in	2007-03-04 23:34:32.000000000 +0100

 @@ -2522,7 +2522,7 @@

  # FIXME: writing proper dependencies for this is a *LOT* of work.

  libbackend.o : $(OBJS-common:.o=.c) $(out_file) \

    insn-config.h insn-flags.h insn-codes.h insn-constants.h \

 -  insn-attr.h  $(DATESTAMP) $(BASEVER) $(DEVPHASE)

 +  insn-attr.h  $(DATESTAMP) $(BASEVER) $(DEVPHASE) gcov-iov.h

  	$(CC) $(ALL_CFLAGS) $(ALL_CPPFLAGS) \

  	  -DTARGET_NAME=\"$(target_noncanonical)\" \

  	  -DLOCALEDIR=\"$(localedir)\" \