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>

 diff -durN gcc-4.4.0.orig/include/libiberty.h gcc-4.4.0/include/libiberty.h

 --- gcc-4.4.0.orig/include/libiberty.h	2008-06-24 03:42:31.000000000 +0200

 +++ gcc-4.4.0/include/libiberty.h	2009-05-27 21:38:24.000000000 +0200

 @@ -595,8 +595,11 @@

  /* Like sprintf but provides a pointer to malloc'd storage, which must

     be freed by the caller.  */

 +/* asprintf may be declared as a macro by glibc with __USE_FORTIFY_LEVEL.  */

 +#ifndef asprintf

  extern int asprintf (char **, const char *, ...) ATTRIBUTE_PRINTF_2;

  #endif

 +#endif

  #if !HAVE_DECL_VASPRINTF

  /* Like vsprintf but provides a pointer to malloc'd storage, which