Support arm64ec targets

### Brief Issue Summary

ARM64EC requires a different visual studio configuration. This documentation describes what to put in the preset file: https://devblogs.microsoft.com/cppblog/arm64ec-support-in-visual-studio/

```
"architecture": {
"value": "arm64ec",
"strategy": "external"
}
```

But when I try to build, the VS configuration used underneath (LIB environment variable, for instance) seems to point to x86.

### CMake Tools Diagnostics

I'd rather not post here. I can provide them on demand.

### Debug Log

No log. The feature seems to not be supported. I searched for "arm64ec" in the entire issue database and repo, and found no hits. This is a request to implement this (or to set me straight if I'm mistaken in any way).