Incorrectly skipped projects with `FastUpToDate: No build outputs defined.`

## Visual Studio Version

17.0.x and 17.1 Preview 1 & 2

## Summary
When building [the following solution](https://github.com/unoplatform/uno/blob/master/src/Uno.UI.sln), with [filters like this one](https://github.com/unoplatform/uno/blob/master/src/Uno.UI-Wasm-only.slnf), some projects tend to be skipped during build, either silently, or with the following message (even when explicitly being asked to build):
```
11>FastUpToDate: No build outputs defined. (Uno.UI.Wasm)
11>FastUpToDate: Project is up to date. (Uno.UI.Wasm)
```

## Steps to Reproduce

1. Clone https://github.com/unoplatform/uno @ https://github.com/unoplatform/uno/commit/4f08e8a0c531200980ac3a552e1f05438e0da618
2. Copy `src/crosstargeting_override.props.sample` to `src/crosstargeting_override.props`
3. In `src/crosstargeting_override.props`, uncomment `UnoTargetFrameworkOverride` and set it to netstandard2.0
4. Open `src/Uno.UI-Wasm-only.slnf`
5. Build the `SamplesApp.Wasm` project explicitly.

## Expected Behavior
The build succeeds reliably.

## Actual Behavior
The build may fail to process the `Uno.UI.Tasks`, `Uno.UI.Wasm`, `Uno.UI.FluentTheme.v1.Wasm`, `Uno.UI.FluentTheme.v2.Wasm` and `Uno.UI.FluentTheme.Wasm` specifically. The other projects generally don't fail.

As a result dependents fail to build because of a missing assembly.

## Workaround
Workarounds include:
- Manually deleting the `.vs` folder
- `git clean -fdx`
- Restart VS and build the faulty projects explicitly.

## User Impact
Not able to reliably build a solution.