simplify dummy rules

Use true instead of echo >/dev/null -- same effect, less bytes.
Signed-off-by: Kir Kolyshkin <kir@openvz.org>
Signed-off-by: Pavel Emelyanov <xemul@parallels.com>

scripts/Makefile.build

@@ -230,7 +230,7 @@ cleanup-y += $(_cleanup-y)
 .PHONY: all clean
 
 all: $(_all)
-	@echo > /dev/null
+	@true
 
 clean:
 	$(E) "  CLEANUP " $(obj)

scripts/Makefile.rules

@@ -49,4 +49,4 @@ endef
 ## together with .SUFFIXES not cleaned, this
 ## will slow down the build procedure
 scripts/Makefile.rules::
-	@echo > /dev/null
+	@true

scripts/Makefile.version

@@ -22,4 +22,4 @@ $(VERSION_HEADER): Makefile scripts/Makefile.version
 ## together with .SUFFIXES not cleaned, this
 ## will slow down the build procedure
 scripts/Makefile.version::
-	@echo > /dev/null
+	@true

test/zdtm/lib/Makefile

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