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>
(transplanted from a0924619112015bdaa81a0a2313d21ef38607bc2)

# ia64 specific config options

# depends on EXPERIMENTAL

config ARCH_ia64

    select ARCH_SUPPORTS_64

    select ARCH_DEFAULT_64

    select ARCH_USE_MMU

    select ARCH_SUPPORTS_BOTH_ENDIAN

    help

      The ia64 architecture, as defined by:

        http://www.intel.com/design/itanium/arch_spec.htm