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: ../crosstool-NG/ct-ng.trunk/patches/binutils/2.19/110-RPATH_ENVVAR-smack.patch

-= BEGIN original header =-

Original patch from Gentoo:

gentoo/src/patchsets/binutils/2.19/08_all_binutils-RPATH_ENVVAR-smack.patch

http://sourceware.org/ml/binutils/2007-07/msg00401.html

http://sourceware.org/bugzilla/show_bug.cgi?id=4970

-= END original header =-

diff -durN binutils-2.19.1.orig/configure binutils-2.19.1/configure

--- binutils-2.19.1.orig/configure	2008-09-04 04:18:16.000000000 +0200

+++ binutils-2.19.1/configure	2009-03-08 11:57:00.000000000 +0100

@@ -5601,6 +5601,7 @@

   *-*-mingw* | *-*-cygwin ) RPATH_ENVVAR=PATH ;;

   *) RPATH_ENVVAR=LD_LIBRARY_PATH ;;

 esac

+RPATH_ENVVAR="cant_touch_this_nah_nah_nah"

 # On systems where the dynamic library environment variable is PATH,

 if test "$RPATH_ENVVAR" = PATH; then