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/configure.ac strace-4.5.15/configure.ac

 --- strace-4.5.15.orig/configure.ac	2007-07-14 19:25:25.000000000 +0200

 +++ strace-4.5.15/configure.ac	2007-07-14 19:27:35.000000000 +0200

 @@ -91,14 +91,14 @@

  	arch=hppa

  	AC_DEFINE([HPPA], 1, [Define for the HPPA architecture.])

  	;;

 -sh)

 -	arch=sh

 -	AC_DEFINE([SH], 1, [Define for the SH architecture.])

 -	;;

  sh64)

  	arch=sh64

  	AC_DEFINE([SH64], 1, [Define for the SH64 architecture.])

  	;;

 +sh*)

 +	arch=sh

 +	AC_DEFINE([SH], 1, [Define for the SH architecture.])

 +	;;

  x86?64*)

  	arch=x86_64

  	AC_DEFINE([X86_64], 1, [Define for the AMD x86-64 architecture.])