Simple OpenBSD build fix

Index: Makefile
--- Makefile.orig
+++ Makefile
@@ -17,7 +17,7 @@ wev: wev.c shm.c xdg-shell-protocol.h xdg-shell-protoc
 	$(CC) $(CFLAGS) \
 		-g -std=c11 -I. \
 		-o wev wev.c shm.c xdg-shell-protocol.c \
-		$(LIBS) -lrt
+		$(LIBS)
 
 wev.1: wev.1.scd
 	$(SCDOC) < wev.1.scd > wev.1
@@ -33,8 +33,8 @@ DESTDIR?=
 install: wev
 	mkdir -p $(DESTDIR)$(BINDIR)
 	mkdir -p $(DESTDIR)$(MANDIR)/man1
-	install -m755 wev $(DESTDIR)$(BINDIR)/wev
-	install -m644 wev.1 $(DESTDIR)$(MANDIR)/man1/wev.1
+	install -c -m755 wev $(DESTDIR)$(BINDIR)/wev
+	install -c -m644 wev.1 $(DESTDIR)$(MANDIR)/man1/wev.1
 
 clean:
 	rm -f wev wev.1 xdg-shell-protocol.h xdg-shell-protocol.c