[cmake-developers] PRE_BUILD misconception

[Sebastian Holtermann]

It seems that in CMake 3.9/AUTOGEN the VS generator uses the *_autogen
target more often than necessary (it could use PRE_BUILD instead).

Let's assume a target `B` that depends on
 - a *GENERATED* file `FA`
 - a linked library `LA`
 - a utility target `TA` (via `add_dependencies()`)

Using the VS generator, will `FA`, `LA` and `TA` be built completely before
target B executes it's PRE_BUILD?

I'm asking because it's important to know when to PRE_BUILD can be used for 
AUTOGEN.

-Sebastian