x11/wmenu: Fix build with llvm16

Approved by:	portmgr (blanket)
Sponsored by:	The FreeBSD Foundation

x11/wmenu/Makefile

@@ -29,4 +29,10 @@ LDFLAGS+=	`pkg-config --libs epoll-shim`
 PLIST_FILES=	bin/wmenu \
 		man/man1/wmenu.1.gz
 
+.include <bsd.port.options.mk>
+
+.if ${OPSYS} == FreeBSD && ${OSVERSION} >= 1400097
+CFLAGS+=	-D__BSD_VISIBLE -D__XSI_VISIBLE
+.endif
+
 .include <bsd.port.mk>