json-c: fix icecc compilation

json-c: fix icecc compilation

Skip -Werror to make it possible to compile this recipe with ICECC else
all fallthrough comments will be removed since we pre-process the files
on the host before sending them to the compile nodes which then cause
errors because of default -Werror switch.

Fixes: caf64f85b5c5 ("json-c: update 0.13.1 - > 0.14")
Signed-off-by: Marco Felsch <m.felsch@pengutronix.de>
Signed-off-by: Alexandre Belloni <alexandre.belloni@bootlin.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>