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>

 # mingw options

 # depends on MINGW32

 config LIBC_mingw

     bool

     select LIBC_SUPPORT_WIN32THREADS

     help

       The de-facto standard for Mingw distributions.

 choice

     bool

     prompt "Mingw runtime version"

 # Don't remove next line

 # CT_INSERT_VERSION_BELOW

 config MINGWRT_V_3_18

     bool

     prompt "3.18"

 config MINGWRT_V_select

     bool

     prompt "Other version"

 endchoice

 config MINGWRT_VERSION

     string

     prompt "Mingw runtime version" if MINGWRT_V_select

 # Don't remove next line

 # CT_INSERT_VERSION_STRING_BELOW

     default "3.18" if MINGWRT_V_3_18

     help

       Enter the version number of the mingw runtime files to use