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>

 Enable building a pure soft-float compiler without the need for a software

 floating point library.

 diff -dur gcc-4.0.4.orig/gcc/config.gcc gcc-4.0.4/gcc/config.gcc

 --- gcc-4.0.4.orig/gcc/config.gcc	2007-02-02 19:12:28.000000000 +0100

 +++ gcc-4.0.4/gcc/config.gcc	2007-02-02 19:12:07.000000000 +0100

 @@ -677,7 +677,7 @@

  		tm_defines="TARGET_BIG_ENDIAN_DEFAULT=1 $tm_defines"

  		;;

  	esac

 -	tmake_file="${tmake_file} arm/t-arm arm/t-linux"

 +	tmake_file="${tmake_file} arm/t-arm arm/t-linux arm/t-arm-elf"

  	extra_parts="crtbegin.o crtbeginS.o crtend.o crtendS.o"

  	gnu_ld=yes

  	;;