spin.exe depends on vcruntime140.dll

[jandubois]

Let's see if upstream will provide a statically linked version; then we should update to use that one (see spinframework/spin#1504).

If they decide not to do this, then we should at least add a diagnostic to check if the DLL is available via the PATH and show a warning if it isn't.

The same issue applies to the js2wasm plugin as well, but not the kube plugin. Other plugins are likely affected as well, if they are written in Rust, but I haven't checked.