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>

 #!@@CT_bash@@

 # What we need:

 #  - the .config file

 # Parse the tools' paths configuration

 . "${CT_LIB_DIR}/paths.mk"

 # We'll need the stdout later, save it

 exec 7>&1

 # Parse the common functions

 . "${CT_LIB_DIR}/scripts/functions"

 # Don't care about any log file

 exec >/dev/null

 rm -f "${tmp_log_file}"

 # Parse the configuration file

 . .config

 # Parse architecture and kernel specific functions

 . "${CT_LIB_DIR}/scripts/build/arch/${CT_ARCH}.sh"

 . "${CT_LIB_DIR}/scripts/build/kernel/${CT_KERNEL}.sh"

 # Build CT_TARGET

 CT_DoBuildTargetTuple

 # All this for this single echo... :-( Sigh, I'll have to re-arrange things...

 echo "${CT_TARGET}" >&7