[Development] Build system for Qt 6

[Nikolai Kosjar]

On 10/29/18 1:17 PM, Lars Knoll wrote:
> Given that we are confident we can build Qt 6 with cmake, I believe that it makes most sense to follow down that route. 

Just some observation:

LLVM/Clang is a bigger project using CMake for some longer time and 
coincidentally, just now, there is a discussion whether they should add 
GN build files to their repositories as, let me quote:

"""
cmake is great for many use cases, but in my opinion local day-to-day 
development isn't one of them.
"""

Clang: https://lists.llvm.org/pipermail/cfe-dev/2018-October/060006.html
LLVM: https://lists.llvm.org/pipermail/llvm-dev/2018-October/127342.html

Nikolai