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: mpf_set_str.c.4.diff

-= BEGIN original header =-

-= END original header =-

diff -durN gmp-4.2.4.orig/mpf/set_str.c gmp-4.2.4/mpf/set_str.c

--- gmp-4.2.4.orig/mpf/set_str.c	2008-08-25 16:11:37.000000000 +0200

+++ gmp-4.2.4/mpf/set_str.c	2009-03-08 18:36:16.000000000 +0100

@@ -137,7 +137,12 @@

       c = (unsigned char) *++str;

     }

+  /* Default base to decimal.  */

+  if (base == 0)

+    base = 10;

+

   exp_base = base;

+

   if (base < 0)

     {

       exp_base = 10;

@@ -165,10 +170,6 @@

 	return -1;

     }

-  /* Default base to decimal.  */

-  if (base == 0)

-    base = 10;

-

   /* Locate exponent part of the input.  Look from the right of the string,

      since the exponent is usually a lot shorter than the mantissa.  */

   expptr = NULL;