Consider ceasing using Ninja on Mac and Linux

[kuzminrobin]

Currently QIR RT has CMake use Ninja build agent.
I believe that Ninja is only required on Windows (without it CMake always uses MSVC compiler instead of clang), and is not required on Mac and Linux (I tested that when compiling NativeSimulator with clang).
Consider not using Ninja with CMake and removing Ninja from prerequisites on Mac and Linux for QIR RT.

[swernli]

I would prefer that we use the same generator across all three platforms to have a uniform configuration experience. Right now we don't do much in the way of configuration for the generator step, but if we needed to then it would be better to be using the same flags and options across platforms even if the actual values on the platforms need to be different.

By way of background, when no generator is selected, cmake uses the default generator for the current platform. On Windows, the default generator is Visual Studio 16 2019 while on Linux and Mac it is Unix Makefiles. This is why switching compilers was challenging without Ninja on Windows, as the Visual Studio 16 generator uses different flags and options as compared to other generators and will prefer compilers present in the local systems VS installation. The Ninja generator tends to be recommended for setting up builds that run cross platform since it is supported across all major platforms, and is specifically called out in the CMake documentation (see the docs for the cmake -g option). Ninja itself is used by many cross-platform projects, including LLVM. See https://ninja-build.org/ and https://ninja-build.org/manual.html for more info.

[swernli]

As an additional data point, the dotnet runtime uses Ninja as its default cmake generator for maximum cross-platform compatibility. See their requirements in the docs: https://github.com/dotnet/runtime/blob/main/docs/workflow/requirements/windows-requirements.md#ninja
and related issue announcing it:
dotnet/runtime#50794