PR #640 causes very annoying .NET SDK not found

### Usage Information

Fallout as developer (not consumer) via Rider

### Description

The PR #640 causes a very annoying "bug". It does resist to load the solution if 10.0.302 SDK isn't installed.

Running `.\build.ps1` installs it into .fallout/temp/dontet-{win,unix}, but this does not help Rider. Of course you could change in the Rider settings the SDK search path, but you have to do this every SDK update.

### Reproduction Steps

- Having .NET SDK 10.0.400 installed and no 10.0.3xx
- Checkout develop

### Expected Behavior

Solution loads in Rider/VS

### Actual Behavior

Does not load

### Regression?

You could argue: yes (because rollForward: latestMinor got this)

### Known Workarounds

- Changing rollForward back to "latestMinor"
- Update global.json to this content:
```json
{
"sdk": {
"version": "10.0.302",
"rollForward": "latestPatch",
"paths": [
".fallout/temp/dotnet-win",
".fallout/temp/dotnet-unix",
"$host$"
]
}
}
```

This tells Rider/VS/IDE to look into the locally install directories first and then what's installed on the host.
Works locally, in CI/CD with pre-installed SDK and in CI/CD with no matching SDK installed (since build.{sh,ps1} installs it and will be picked up)

I propose to add this to the global json, since it doesn't hurt anyone, but restores a fallback path for local dev.

### Could you help with a pull-request?

Yes