cc/gcc: allow CC_EXTRA_CONFIG_ARRAY on baremetal

The final bare-metal compiler is built using the core backend.
Currently the core uses the CC_CORE_EXTRA_CONFIG_ARRAY variable.

While this works as supposed to, this can leave the user puzzled
in the menuconfig, since all he can see is the core options, not
the final options.

Only show the core options if any of the core passes are needed,
and use the final options in the core-backend if we're issuing
the bare-metal compiler.

Signed-off-by: Cody P Schafer <dev@codyps.com>
[yann.morin.1998@free.fr: hide core options if no core pass needed;
use final option in core backend if issuing the bare-metal compiler]
Signed-off-by: "Yann E. MORIN" <yann.morin.1998@free.fr>
Message-Id: <22181e546ba746202489.1399688067@localhost>
Patchwork-Id: 347586

 This is the README for crosstool-NG

 Crosstool-NG follows the autoconf dance. So, to get you

 kick-started, just run:

     ./configure --help

 If you are using a development snapshot, you'll have to

 create the configure script, first. Just run:

     ./bootstrap

 You will find the documentation in the directory 'docs'.

 Here is a quick overview of what you'll find there:

   0 - Table of content

   1 - Introduction

   2 - Installing crosstool-NG

   3 - Configuring a toolchain

   4 - Building the toolchain

   5 - Using the toolchain

   6 - Toolchain types

   7 - Contributing

   8 - Internals

   A - Credits

   B - Known issues

   C - Misc. tutorials

 You can also point your browser at:

   http://crosstool-ng.org/

 Aloha!