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)

 Index: ltrace-0.5.3/configure

 ===================================================================

 --- ltrace-0.5.3/configure

 +++ ltrace-0.5.3/configure

 @@ -78,7 +78,10 @@ fi

  rm -f conftest.c a.out

  CFLAGS='-g -O2'

 -LIBS='-lelf -lsupc++ -liberty '

 +LIBS='-lelf'

 +[ -n "$HAVE_LIBSUPC__" ] && LIBS="$LIBS -lsupc++"

 +[ -n "$HAVE_LIBIBERTY" ] && LIBS="$LIBS -liberty"

 +

  INSTALL='install -c'

  iquote='-iquote '

  iquoteend=''