cc/gcc: build core compilers for canadian

Currently, we rely on an existing external cross-compiler targetting
the target, to build the C library.

This can pause quite a few problems if that compiler is different from
the one we are building, because it could introduce some ABI issues.

This patch removes this dependency, by building the core compilers
as we do for standard cross, and also by building the binutils and
gcc, for running on the build machine.

This means we no longer need to offer the cross-sompiler selection in
the menuconfig.

Signed-off-by: "Yann E. MORIN" <yann.morin.1998@anciens.enib.fr>

# mingw options

## depends on MINGW32

##

## 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