ci: remove unused Windows ninja install and modernize CMake invocation

[kevmoo]

• Remove the unused choco install ninja step on windows-latest (added in a08df5c9 but never used since Windows CMake defaults to Visual Studio).
• Modernize CMake configuration across all platforms by using -S . -B out instead of manually creating out/ and setting working-directory: out.

Split out from #2717.

[sbc100]

IIRC the main thing this change does is convert the windows build to use Ninja. Previously we were using the cmake default which on windows means Visual Studio.

Are we sure we want to use Ninja on Windows rather than Visual Studio.. its seems fine I guess (since the underlying compiler is still MSVC), but most windows users will use Visual Studio I imagine?

In any case the Fix the Windows build step missing the -G Ninja part of the description seem wrong. Can you update that?

[kevmoo]

Good catch! The only reason I originally added -G Ninja on Windows was because choco install ninja was already present in build.yml (from a08df5c9), so I assumed Ninja was intended on Windows too.

Keeping the default Visual Studio generator on Windows makes much more sense since that's what Windows users actually use. Updated this PR to:

• Keep the default Visual Studio CMake generator on Windows (reverting the Ninja/MSVC workarounds).
• Remove the unused choco install ninja step on Windows.
• Keep the -S . -B out CMake modernization across all platforms.

[sbc100]

lgtm.

Can you update the PR description to be the one you want to use when this lands. i.e. maybe remove the "Keep the default Visual Studio.." part?

[kevmoo]

Updated the step name to cmake version and updated the PR description for landing—thanks!