gcc: use default C++ mode for host compiler

GCC 6 changed the default C++ mode from gnu++98 to gnu++14. This change
caused some packages to stop building. GCC 6 has been out for 4 years.

Affected software should have been fixed by now. Remaining software
should be updated, purged, or have its call to gcc changed to include
this individually.

Signed-off-by: Ian Leonard <antonlacon@gmail.com>

packages/lang/gcc/package.mk

@@ -69,7 +69,6 @@ PKG_CONFIGURE_OPTS_HOST="$GCC_COMMON_CONFIGURE_OPTS \
                          $GCC_OPTS"
 
 pre_configure_host() {
-  export CXXFLAGS="$CXXFLAGS -std=gnu++98"
   unset CPP
 }