Fix @persistent@ substitution logic.

Just handle @persistent@ as a normal boolean.
On 11/06/2014 07:41 AM, Alexandre Detiste wrote:
>> @@ -159,6 +157,9 @@ $(builddir)/units/cron-boot.service: $(srcdir)/units/cron-boot.service.in
>>  
>>  $(builddir)/units/cron-%.timer: $(srcdir)/units/cron-schedule.timer.in
>>  	$(call in2out,$<,$@,$*)
>> +ifneq ($(enable_persistent),yes)
>> +	sed -i -e '/^Persistent=/d' $@
>> +endif
>>  
> 
> shouldn't this shifter to the right (for readability) ?

Not in make...