NMake Builds: Fix linking on Rust 1.70.0 or later

Hi,

Thanks to @kleisauke, it was found that we need to link to ntdll.lib for Rust 1.70.0 (or nightly-2023-03-21) or later 1, which was sadly not documented, when building the librsvg DLL. So, this MR extends from the recent additions on checking the default Rust toolchain to check whether we need to link to ntdll.lib (which can be misleading as the Microsoft docs mentioned that ntdll.lib only comes with the WDK (Windows Drivers Kit), but actually ships with the Windows 8.1/10/11 SDKs.

This will fix issue #968 (closed).

With blessings, thank you!