[Development] better compile-time os detection

[Christian Kandeler]

On 7/21/26 6:45 AM, EXT Tim Blechmann via Development wrote:
> working on some way of OS detection without preprocessor, there are a
> few shortcomings of QOperatingSystemVersion::OSType: most notably, it's
> impossible to dispatch linux-specific code, as there is no OSType::Linux
> (by design, as Android/OHOS are linux based as well). thiago recommended
> to discuss this on the list.

[ ... ]
> B: map OS defines to constexpr bool variables

This has the advantage of guaranteeing that everything is covered. With 
the other approaches, someone will always miss something.

Christian