Override for ELF. Override .s.o suffix rule.

sys/boot/i386/btx/lib/Makefile

@@ -1,6 +1,7 @@
-#	$Id:$
+#	$Id: Makefile,v 1.1 1998/09/14 10:37:00 rnordier Exp $
 
 OBJS=		btxcsu.o btxsys.o btxv86.o
+AFLAGS+=	-elf
 LDFLAGS+=	-elf
 CLEANFILES+=	crt0.o
 INTERNALLIB=	true
@@ -14,3 +15,6 @@ crt0.o: ${OBJS}
 	${LD} ${LDFLAGS} -i -o ${.TARGET} ${OBJS}
 
 .include <bsd.lib.mk>
+
+.s.o:
+	${AS} ${AFLAGS} -o ${.TARGET} ${.IMPSRC}