Fortified headers don't seem to like _GNU_SOURCE in this case,
but we can remove that define since it's not needed. Add a patch
for LEDE until a new horst version is released.

Signed-off-by: Bruno Randolf <br1@einfach.org>

Signed-off-by: Bruno Randolf <br1@einfach.org>

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

4.1 has an important bugfix for platforms (such as ARM cns3xxx) where "char"
does not default to "signed char" and other bugfixes.

Also build with debugging enabled (-D flag) to enable debugging, the size
increase is just +336B (on platform au1000).

Signed-off-by: Bruno Randolf <br1@einfach.org>