Tobias Hunger authored Nov 28, 2018 and Brad King committed Jan 10, 2019

Allow to force moc/rcc/uic compiler used for AUTO(MOC|RCC|UIC).

Setting these properties is only necessary if you are going to do
strange things like build these tools as part of your own build system.

Setting these properties will also prevent cmake from testing the
binary: It is user-provided and assumed to be valid.