zdtm: suppress the message "Nothing to be done for 'all'"

Execute zdtm/live/static/env00
make[1]: Nothing to be done for `all'.
make[1]: Nothing to be done for `all'.
./env00 --pidfile=env00.pid --outfile=env00.out --envname=ENV_00_TEST
Dump 18232
Restore
Check results 18232
14:53:59.615: 18232: PASS
Test: zdtm/live/static/env00, Result: PASS
ZDTM tests PASS.
Signed-off-by: Andrey Vagin <avagin@openvz.org>
Signed-off-by: Pavel Emelyanov <xemul@parallels.com>

test/zdtm/lib/Makefile

@@ -14,6 +14,7 @@ DEPEND.c = $(COMPILE.c) -MM -MP
 	$(DEPEND.c) $(OUTPUT_OPTION) $<
 
 all:	$(LIB)
+	@echo > /dev/null
 install: all
 
 $(LIB):	$(LIB)(${LIBOBJ})