[Development] Proposing CMake as build tool for Qt 6

[Tor Arne Vestbø]

> On 6 Jun 2019, at 15:41, Simon Hausmann <Simon.Hausmann at qt.io> wrote:
> 
> Hi,
> 
> I believe the code signing part is covered by existing CMake xcode support, as it is also for macOS.
> 
> The support for fat binaries is something I don't have hands-on experience, but the upstream documentation suggests support for it on macOS, iOS, etc.:
> 
>     https://cmake.org/cmake/help/latest/variable/CMAKE_OSX_ARCHITECTURES.html
> 
> This appears to result in multiple -arch parameters on the command line when calling the compiler.

That’s one step, and will let you create e.g. a fat binary with x86_64 and i386, or armv7 and armv8.

The next step is being able to create a x86_64 + armv8 binary, and for that CMake needs to learn how to use -Xarch to pass two sets of SDKs and deployment target arguments:

https://github.com/qt/qtbase/blob/53d62b8fcbb639bd625777c8f1c01764445fb1c4/mkspecs/features/mac/default_post.prf#L165

Tor Arne