Json related errors while building

For anyone running a recent version of golang you might get some errors related to the JSON package in alias.go. This is a known issue: https://github.com/tailscale/tailscale/issues/20254

The fix is on windows to set the following environment variable:
```
$env:GOEXPERIMENT = "nojsonv2"
```

Hopefully this helps someone that faces the same issue :)