[CMake] Inserting a dependency before Qt moc is run

[Stephen Kelly]

Aurélien Gâteau wrote:
 
>>  http://cmake.org/gitweb?p=cmake.git;a=commitdiff;h=ae016fa8a
> 
> Thanks, how would one make use of this change if it gets in?

I've reverted it for now as it breaks the KF5 build.

Usage would be

 add_custom_target(cust ...)
 set_property(TARGET gwenviewPlugin1 
   APPEND PROPERTY AUTOGEN_TARGET_DEPENDS cust
 )

Thanks,

Steve.