package/redis: disable -Werror

Disable -Werror to avoid the following build failure raised since bump
to version 7.2.1 in commit d49f53f8aaf0bff9c8d04c16485c844fef2832d0 and
https://github.com/redis/redis/commit/8e138ba44fc3eb676c0f31faac19d1acc6a4c7ed:

In function 'hi_sdsll2str',
    inlined from 'hi_sdsfromlonglong' at sds.c:500:15:
sds.c:457:12: error: writing 1 byte into a region of size 0 [-Werror=stringop-overflow=]
  457 |         *s = *p;
      |         ~~~^~~~

Fixes: d49f53f8aaf0bff9c8d04c16485c844fef2832d0
 - http://autobuild.buildroot.org/results/fdc9f940b348430cb4da8efecc5cc047b21df281
 - http://autobuild.buildroot.org/results/e5747674d52b065203a0442f7cab13e8be5f426b

Signed-off-by: Fabrice Fontaine <fontaine.fabrice@gmail.com>
Signed-off-by: Peter Korsgaard <peter@korsgaard.com>

package/redis/redis.mk

@@ -30,7 +30,7 @@ endif
 # https://github.com/antirez/redis/pull/609).  We set PREFIX
 # instead.
 REDIS_BUILDOPTS = $(TARGET_CONFIGURE_OPTS) \
-	PREFIX=$(TARGET_DIR)/usr MALLOC=libc
+	PREFIX=$(TARGET_DIR)/usr MALLOC=libc WARNINGS=
 
 ifeq ($(BR2_PACKAGE_SYSTEMD),y)
 REDIS_DEPENDENCIES += systemd