mkrules.mk: Pass $(COPT) to link stage.

In generalize case, optimization options should be passed to all stages of
the build process.

py/mkrules.mk

@@ -73,7 +73,7 @@ all: $(PROG)
 
 $(PROG): $(OBJ)
 	$(ECHO) "LINK $@"
-	$(Q)$(CC) -o $@ $(OBJ) $(LIB) $(LDFLAGS)
+	$(Q)$(CC) $(COPT) -o $@ $(OBJ) $(LIB) $(LDFLAGS)
 ifndef DEBUG
 	$(Q)$(STRIP) $(STRIPFLAGS_EXTRA) $(PROG)
 endif