Add the ability to compile to windows ARM

[kevaundray]

This is not strictly needed, since most clients do not support ARM on windows.

The blockers for this are mainly the fact that arm on windows seems to only have first class support for msvc and mavc doesn't seem to work well with nim.

More investigation would definitely be needed, I may have missed the tier1/2 gnu target for ARM that we could use or maybe we should just do msvc on windows.

[kevaundray]

We have aarch64-pc-windows-gnullvm but unsure about its stability -- also not tier1/2