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>

 2008-04-28  Hiroki Kaminaga  <kaminaga@sm.sony.co.jp>

 	[BZ 6740]

 	nptl/sysdeps/powerpc/tcb-offsets.sym (PRIVATE_FUTEX_OFFSET):

 	Guard sym definition with #ifndef __ASSUME_PRIVATE_FUTEX.

 --- a/nptl/sysdeps/powerpc/tcb-offsets.sym

 +++ b/nptl/sysdeps/powerpc/tcb-offsets.sym

 @@ -15,4 +15,6 @@

  PID				thread_offsetof (pid)

  TID				thread_offsetof (tid)

  POINTER_GUARD			(offsetof (tcbhead_t, pointer_guard) - TLS_TCB_OFFSET - sizeof (tcbhead_t))

 +#ifndef __ASSUME_PRIVATE_FUTEX

  PRIVATE_FUTEX_OFFSET		thread_offsetof (header.private_futex)

 +#endif