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>

 --- glibc-2.7/sysdeps/unix/sysv/linux/kernel-features.h	2007-08-14 06:21:09.000000000 +0300

 +++ glibc-2.7/sysdeps/unix/sysv/linux/kernel-features.h.new	2008-07-23 07:05:20.000000000 +0300

 @@ -449,8 +449,7 @@

     and on Alpha just after 2.6.22-rc1.  */

  #if __LINUX_KERNEL_VERSION >= 0x020611 \

      && ((!defined __sh__ && !defined __alpha__) \

 -	|| (__LINUX_KERNEL_VERSION >= 0x020613 && defined __sh__) \

 -	|| (__LINUX_KERNEL_VERSION >= 0x020617 && defined __alpha__))

 +	|| (__LINUX_KERNEL_VERSION >= 0x020613 && defined __sh__))

  # define __ASSUME_ATFCTS	1

  #endif