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)

 #!/bin/sh

 # this wrapper will not work under BSD systems or others

 # not containig the GNU readlink.

 # Under those, wrapper.c will forcibly be used

 # regardless of the config file setting.

 canonicalizedname=$(readlink -nm "${0}")

 dirname="$(dirname "${canonicalizedname}")"

 basename="$(basename "${canonicalizedname}")"

 ld_lib_path="$(dirname "${dirname}")/lib"

 case ":${LD_LIBRARY_PATH}:" in

     *":${ld_lib_path}:"*)   ;;

     *)  LD_LIBRARY_PATH="${ld_lib_path}${LD_LIBRARY_PATH:+:${LD_LIBRARY_PATH}}";;

 esac

 export LD_LIBRARY_PATH

 exec "${dirname}/.${basename}" "$@"