MinGW builds: Fix linking on Rust 1.70.0 and later

Hi,

This attempts to fix builds with MSYS2/mingw-w64 when building against Rust 1.70.0 or later. Since I am not very knowledgeable at all on autotools scripting, I am just following what is done for the other Windows libraries that are linked in to check for and link to -lntdll if we are using Rust 1.70.0 or later, so this is essentially a less-sophisticated fix for the MSYS2 side for issue #968 (closed), which should also fix the msys2-mingw64 CI (which is now failing as msys2/mingw-w64 updated to Rust 1.70.0).

With blessings, thank you!