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/gentoo/66_all_gcc43-pr25343.patch

http://gcc.gnu.org/PR25343

sniped from Debian

2008-04-27  Roman Zippel <zippel@linux-m68k.org>

	* config/host-linux.c (TRY_EMPTY_VM_SPACE): Define for __mc68000__.

diff -durN gcc-4.3.1.orig/gcc/config/host-linux.c gcc-4.3.1/gcc/config/host-linux.c

--- gcc-4.3.1.orig/gcc/config/host-linux.c	2007-08-02 12:49:31.000000000 +0200

+++ gcc-4.3.1/gcc/config/host-linux.c	2008-06-10 14:58:28.000000000 +0200

@@ -84,6 +84,8 @@

 # define TRY_EMPTY_VM_SPACE	0x8000000000

 #elif defined(__sparc__)

 # define TRY_EMPTY_VM_SPACE	0x60000000

+#elif defined(__mc68000__)

+# define TRY_EMPTY_VM_SPACE	0x40000000

 #else

 # define TRY_EMPTY_VM_SPACE	0

 #endif