This is just like gnome/control-center. It needs C99. ok?
--Kurt Index: Makefile =================================================================== RCS file: /cvs/ports/x11/mate/control-center/Makefile,v retrieving revision 1.21 diff -u -p -r1.21 Makefile --- Makefile 21 Mar 2020 16:14:54 -0000 1.21 +++ Makefile 28 Mar 2020 05:01:57 -0000 @@ -46,4 +46,6 @@ FAKE_FLAGS= sysconfdir=${PREFIX}/share/ CONFIGURE_STYLE= gnu +CFLAGS += -std=gnu99 + .include <bsd.port.mk>