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>

 diff -ru glibc-2.3.6/elf/Makefile glibc-2.3.6.patched/elf/Makefile

 --- glibc-2.3.6/elf/Makefile	2010-05-02 18:58:38.000000000 -0400

 +++ glibc-2.3.6.patched/elf/Makefile	2010-05-02 18:54:54.000000000 -0400

 @@ -292,7 +292,7 @@

  		  $(LDFLAGS-rtld) -Wl,-z,defs -Wl,--verbose 2>&1 |	\

  		  LC_ALL=C \

  		  sed -e '/^=========/,/^=========/!d;/^=========/d'	\

 -		      -e 's/\. = 0 + SIZEOF_HEADERS;/& _begin = . - SIZEOF_HEADERS;/' \

 +		      -e 's/\. = .* + SIZEOF_HEADERS;/& _begin = . - SIZEOF_HEADERS;/' \

  		  > $@.lds

  	$(LINK.o) -nostdlib -nostartfiles -shared -o $@			\

  		  $(LDFLAGS-rtld) -Wl,-z,defs $(z-now-$(bind-now))	\