Cleanup: replace hard-wired $(AR) 'crv' settings by $(ARFLAGS)

Signed-off-by: Wolfgang Denk <wd@denx.de>
diff --git a/board/ms7750se/Makefile b/board/ms7750se/Makefile
index f81d56c..f02ad0a 100644
--- a/board/ms7750se/Makefile
+++ b/board/ms7750se/Makefile
@@ -25,7 +25,7 @@
 SOBJS	:= lowlevel_init.o
 
 $(LIB):	$(OBJS) $(SOBJS)
-	$(AR) crv $@ $(OBJS) $(SOBJS)
+	$(AR) $(ARFLAGS) $@ $(OBJS) $(SOBJS)
 
 clean:
 	rm -f $(SOBJS) $(OBJS)