package/nftables: disable debug build

nftbles' --with-debug option enables both debugging symbols (with -g)
and debugging macros (with -DDEBUG).

The former are globally driven by the BR2_ENABLE_DEBUG and BR2_DEBUG_n
set of options, and enforced in our toolchain wrapper; the latter should
be driven by the BR2_ENABLE_RUNTIME_DEBUG, but nftables only uses it to
activate an assert-like macro in its json output generator, so we can
well live without that.

So we just unconditionally disable debug in nftables.

Signed-off-by: Peter Seiderer <ps.report@gmx.net>
[yann.morin.1998@free.fr: write a commit log]
Signed-off-by: Yann E. MORIN <yann.morin.1998@free.fr>

package/nftables/nftables.mk

@@ -10,7 +10,7 @@ NFTABLES_SITE = https://www.netfilter.org/projects/nftables/files
 NFTABLES_DEPENDENCIES = libmnl libnftnl host-pkgconf $(TARGET_NLS_DEPENDENCIES)
 NFTABLES_LICENSE = GPL-2.0
 NFTABLES_LICENSE_FILES = COPYING
-NFTABLES_CONF_OPTS = --disable-man-doc --disable-pdf-doc
+NFTABLES_CONF_OPTS = --disable-debug --disable-man-doc --disable-pdf-doc
 NFTABLES_SELINUX_MODULES = iptables
 
 ifeq ($(BR2_PACKAGE_GMP),y)