cc/gcc: fix C++ headers location

In case we build the C++ compiler, we have to tell gcc where to put the C++
headers, or else it will try to # put it in prefix/tuple/include, which we
make a symlink to sysroot/usr/include during the build, and that we delete
(the symlink!) after the build, but gcc will not look in sysroot/usr/inlcude
for C++ headers by default.

Implements a fix suggested by: Bryan Hundven <bryanhundven@gmail.com>

Reported-by: Anthony Foiani <anthony.foiani@gmail.com>
Signed-off-by: "Yann E. MORIN" <yann.morin.1998@anciens.enib.fr>

# ARM specific configuration file

config ARCH_arm

    select ARCH_SUPPORTS_32

    select ARCH_DEFAULT_32

    select ARCH_SUPPORTS_BOTH_MMU

    select ARCH_DEFAULT_HAS_MMU

    select ARCH_SUPPORTS_BOTH_ENDIAN

    select ARCH_DEFAULT_LE

    select ARCH_SUPPORT_ARCH

    select ARCH_SUPPORT_CPU

    select ARCH_SUPPORT_TUNE

    select ARCH_SUPPORT_FPU

    help

      The ARM architecture, as defined by:

        http://www.arm.com/