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>

# Test suite config options

if EXPERIMENTAL

menu "Test suite"

config TEST_SUITE

    bool

    default n

config TEST_SUITE_GCC

    bool

    prompt "GCC test suite"

    depends on EXPERIMENTAL

    default n

    select TEST_SUITE

    help

      Select this option to install the GCC test suite in $CT_PREFIX_DIR/test_suite.

      The GCC test suite includes a collection of various toolchain tests for GCC -

      it utilizes the DejaGnu test framework.

      For some tests a network enabled target with ssh server is required.

      A helper Makefile is provided for running the tests - please see the included 

      README for information on how to run the test suite.

endmenu

endif