Windows has been available for ARM64 on laptops since the end of 2018, but the Surface Pro X released in the end of 2019 made it even more popular

Right now Poco fails to build even the basic components, like Foundation with the amd64_arm64 environment from Visual Studio 2019 or 2022.

We should:

• Add the required _M_ARM64 detection (See [poco] Enable arm64-windows (Fix #5997) microsoft/vcpkg#6182) so at least CMake builds are working
• Add ARM64 to buildwin.cmd