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>

# MIPS specific config options

config ARCH_mips

    select ARCH_SUPPORTS_32

    select ARCH_SUPPORTS_64 if EXPERIMENTAL

    select ARCH_DEFAULT_32

    select ARCH_USE_MMU

    select ARCH_SUPPORTS_BOTH_ENDIAN

    select ARCH_DEFAULT_BE

    select ARCH_SUPPORT_ARCH

    select ARCH_SUPPORT_TUNE

    help

      The MIPS architecture, as defined by:

        http://www.mips.com/