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 -dur strace-4.5.15.orig/signal.c strace-4.5.15/signal.c

 --- strace-4.5.15.orig/signal.c	2007-01-11 23:08:38.000000000 +0100

 +++ strace-4.5.15/signal.c	2007-07-14 19:24:43.000000000 +0200

 @@ -1440,7 +1440,7 @@

  	  	tcp->u_rval = tcp->u_error = 0;

  		if(tcp->u_arg[0] == 0)

  		  	return 0;

 -		tcp->auxstr = sprintsigmask("mask now ", tcp->u_arg[1]);

 +		tcp->auxstr = sprintsigmask("mask now ", tcp->u_arg[1], 0);

  		return RVAL_NONE | RVAL_STR;

  	}

  	return 0;