net-mgmt/nagnu: unbreak on FreeBSD 13+

Build with -fcommon to avoid a duplicate symbol error.

See also:	frlen/nagnu#5
Approved by:	portmgr (build fix blanket)

net-mgmt/nagnu/Makefile

@@ -1,5 +1,6 @@
 PORTNAME=	nagnu
 PORTVERSION=	1.1.3
+PORTREVISION=	1
 CATEGORIES=	net-mgmt
 
 MAINTAINER=	fredrik@min-hemsida.net
@@ -9,9 +10,6 @@ WWW=		https://github.com/frlen/nagnu
 LICENSE=	BSD2CLAUSE
 LICENSE_FILE=	${WRKSRC}/LICENSE
 
-BROKEN_FreeBSD_13=	ld: error: duplicate symbol: errorss
-BROKEN_FreeBSD_14=	ld: error: duplicate symbol: errorss
-
 LIB_DEPENDS=	libcurl.so:ftp/curl
 
 USES=		ncurses
@@ -22,6 +20,7 @@ PLIST_FILES=	bin/nagnu \
 		share/examples/nagnu/nagnu.conf.sample
 
 GNU_CONFIGURE=	yes
+CFLAGS+=	-fcommon
 
 do-install:
 	${INSTALL_PROGRAM} ${WRKSRC}/nagnu ${STAGEDIR}${PREFIX}/bin