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>

 Original patch from gentoo: gentoo/src/patchsets/gcc/4.3.1/uclibc/90_all_103-uclibc-conf-noupstream.patch

 diff -durN gcc-4.3.1.orig/gcc/config.gcc gcc-4.3.1/gcc/config.gcc

 --- gcc-4.3.1.orig/gcc/config.gcc	2008-06-10 14:58:09.000000000 +0200

 +++ gcc-4.3.1/gcc/config.gcc	2008-06-10 14:58:36.000000000 +0200

 @@ -2149,7 +2149,7 @@

          ;;

  sh-*-elf* | sh[12346l]*-*-elf* | sh*-*-kaos* | \

  sh-*-symbianelf* | sh[12346l]*-*-symbianelf* | \

 -  sh-*-linux* | sh[346lbe]*-*-linux* | \

 +  sh*-*-linux* | sh[346lbe]*-*-linux* | \

    sh-*-netbsdelf* | shl*-*-netbsdelf* | sh5-*-netbsd* | sh5l*-*-netbsd* | \

     sh64-*-netbsd* | sh64l*-*-netbsd*)

  	tmake_file="${tmake_file} sh/t-sh sh/t-elf"