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: ../../dev/crosstool-NG/ct-ng.trunk/patches/strace/4.5.17/150-undef-CTL_PROC.patch

 -= BEGIN original header =-

 diff -dur strace-4.5.16.orig/system.c strace-4.5.16/system.c

 -= END original header =-

 diff -durN strace-4.5.17.orig/system.c strace-4.5.17/system.c

 --- strace-4.5.17.orig/system.c	2007-01-17 00:22:36.000000000 +0100

 +++ strace-4.5.17/system.c	2008-10-24 21:30:13.000000000 +0200

 @@ -1612,7 +1612,9 @@

  	{ CTL_KERN, "CTL_KERN" },

  	{ CTL_VM, "CTL_VM" },

  	{ CTL_NET, "CTL_NET" },

 +#ifdef CTL_PROC

  	{ CTL_PROC, "CTL_PROC" },

 +#endif

  	{ CTL_FS, "CTL_FS" },

  	{ CTL_DEBUG, "CTL_DEBUG" },

  	{ CTL_DEV, "CTL_DEV" },