.NET 6 Preview 3 latest build breaks WinForms/WPF apps

[jiangzeng01]

Repro steps:
Install latest build 6.0.100-preview.3.21174.8 from https://github.com/dotnet/installer

Error when running existing WinForms/WPF apps:

Impact:
117 WinForms/WPF apps failed in our AppCompat lab testing caused by this issue.
115 of these apps are real-world third party apps, this means the current latest Preview 3 SDK will break a lot of real-world existing WinForms/WPF apps.

SDK Build info:

.NET SDK (reflecting any global.json):
 Version:   6.0.100-preview.3.21174.8
 Commit:    82a95978c4

Runtime Environment:
 OS Name:     Windows
 OS Version:  10.0.19042
 OS Platform: Windows
 RID:         win10-x64
 Base Path:   C:\Program Files\dotnet\sdk\6.0.100-preview.3.21174.8\

Host (useful for support):
  Version: 6.0.0-preview.3.21167.1
  Commit:  0f64b267ac

.NET SDKs installed:
  6.0.100-preview.3.21174.8 [C:\Program Files\dotnet\sdk]

.NET runtimes installed:
  Microsoft.AspNetCore.App 6.0.0-preview.3.21172.8 [C:\Program Files\dotnet\shared\Microsoft.AspNetCore.App]
  Microsoft.NETCore.App 6.0.0-preview.3.21167.1 [C:\Program Files\dotnet\shared\Microsoft.NETCore.App]
  Microsoft.WindowsDesktop.App 6.0.0-preview.3.21172.2 [C:\Program Files\dotnet\shared\Microsoft.WindowsDesktop.App]

Findings:
In file: "C:\Program Files\dotnet\shared\Microsoft.WindowsDesktop.App\6.0.0-preview.3.21172.2\Microsoft.WindowsDesktop.App.runtimeconfig.json"

{
  "runtimeOptions": {
    "tfm": "net6.0",
    "rollForward": "LatestPatch",
    "framework": {
      "name": "Microsoft.NETCore.App",
      "version": "6.0.0-preview.3.21168.7"
    }
  }
}

Actual Microsoft.NETCore.App installed is:

Microsoft.NETCore.App 6.0.0-preview.3.21167.1 [C:\Program Files\dotnet\shared\Microsoft.NETCore.App]

Microsoft.WindowsDesktop.App.runtimeconfig.json is pointing to a wrong version of Microsoft.NETCore.App.

@dotnet-actwx-bot @dotnet/compat

[dotnet-issue-labeler]

I couldn't figure out the best area label to add to this issue. If you have write-permissions please help me learn by adding exactly one area label.

[jiangzeng01]

This issue should be fixed in 6.0.100-preview.4.21178.2 on main branch, so close