security/ipguard: unbreak on FreeBSD 13+

Build with -fcommon to avoid a duplicate symbol error.

security/ipguard/Makefile

@@ -1,6 +1,6 @@
 PORTNAME=	ipguard
 PORTVERSION=	1.04
-PORTREVISION=	3
+PORTREVISION=	4
 CATEGORIES=	security net
 MASTER_SITES=	http://ipguard.deep.perm.ru/files/ http://deep.perm.ru/files/ipguard/
 
@@ -10,12 +10,10 @@ WWW=		http://ipguard.deep.perm.ru/
 
 LICENSE=	BSD2CLAUSE
 
-BROKEN_FreeBSD_13=	ld: error: duplicate symbol: addr_nosubst
-BROKEN_FreeBSD_14=	ld: error: duplicate symbol: addr_nosubst
-
 LIB_DEPENDS=	libnet.so:net/libnet
 
 USE_RC_SUBR=	${PORTNAME}
+CFLAGS+=	-fcommon
 PORTDOCS=	COPYRIGHT NEWS README README.tcpdump README.log ethers.sample rfc826.txt
 PLIST_FILES=	sbin/ipguard \
 		man/man8/${PORTNAME}.8.gz