fix parallel build

http://bugs.gentoo.org/181043

--- dcron/Makefile
+++ dcron/Makefile
@@ -13,7 +13,8 @@
 PROTOS= protos.h
 DISTTAR= /home/dillon/htdocs/FreeSrc/dcron32.tgz
 
-all:	${PROTOS} crond crontab
+all:	crond crontab
+${OBJS} ${D_OBJS}: ${PROTOS}
 
 crond:	${OBJS}
 	${CC} ${CFLAGS} -o crond ${OBJS} ${LIB} ${LDFLAGS}