chore(msvc): add msvc cmake support

[nitz]

Just two small changes and some CMakeLists.txt additions is all it took to build through Visual Studio 2022.

C&C welcome!

Proposed changes

• Initializes a "potentially uninitialized" pointer that msvc whines about due to /sdl.
• Replaces a VLA with a QVarLengthArray since msvc doesn't support all of C99.
• Adds a check for msvc to CMakeLists.txt, and sets compiler flags that closely match the existing gcc/clang counterparts.
• Adds a few lines to BUILDING.md to elaborate on how to use Visual Studio's built-in cmake support to compile the project.

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A screenshot quite unlikely needed for this, but I took one anyways 😂

Fixes the msvc warning as error due to /sdl.Fixes the msvc warning as error due to /sdl.Fixes the msvc warning as error due to /sdl.Fixes the msvc warning as error due to /sdl.

[pktiuk]

Everything looks good so far. proper MSVC support may be very helpful for developers using Windows.
I have 2 comments:

• I think git history would look better without this style commit
• It would be good to add Compilation via msvc to CI to avoid breaking this support by accident

BTW
When you will think your code will be ready to merge press Ready for review.

[nitz]

I'll go ahead and ready this one up while I look into the cleanest way to add msvc ci. I've set it up several times for .NET projects but not yet done one for C++, or one that uses Qt. (Though the jurplel/install-qt-action@v2 you use looks like it should make that pretty easy!)

[pktiuk]

Great.
I merged these changes now.
I am waiting for another PR with GitHub Action :)

[nitz]

Fantastic! This looks like an excellent thing to work on now too, because my brain is not otherwise having monday morning hahah