[cmake-developers] RFC: CMake precompiled header support and custom compiler based implementation

[Amine Khaldi]

Two requests please:

* The option to use existing headers instead of autogenerated ones.
* Implementing PCH support without additional targets. ReactOS already has like 1000+ targets, and we currently use PCH on almost all of them, so imagine if this official implementation doubles our targets number.

Regards,
Amine.