fix: Define the working directory for add-in discovery (backport #18999)

[mergify]

linked https://github.com/unoplatform/uno.hotdesign/issues/2986

Bugfix

Attempt to define the working directory

What is the current behavior?

Command fails for some user with:

[DEBUG][19:09:17.92]       Failed to get target frameworks of solution 'C:\Temp\Counter\Counter.sln'. This usually indicates that the solution is in an invalid state (e.g. a referenced project is missing on disk). Please fix and restart your IDE (command used: `dotnet build "C:\Temp\Counter\Counter.sln" --target:UnoDumpTargetFrameworks "-p:UnoDumpTargetFrameworksTargetFile=C:\Users\lcaze\AppData\Local\Temp\tmpint0b0.tmp" --verbosity quiet`). (cf. inner exception for more details.)
[DEBUG][19:09:17.92]       System.Exception: Unhandled exception. Microsoft.Build.Shared.InternalErrorException: MSB0001: Internal MSBuild Error: The switch name extracted from either the partially or completely unquoted arg should be the same.
[DEBUG][19:09:17.92]          at Microsoft.Build.Shared.ErrorUtilities.ThrowInternalError(String message, Exception innerException, Object[] args)
[DEBUG][19:09:17.92]          at Microsoft.Build.CommandLine.MSBuildApp.ExtractSwitchParameters(String commandLineArg, String unquotedCommandLineArg, Int32 doubleQuotesRemovedFromArg, String switchName, Int32 switchParameterIndicator)
[DEBUG][19:09:17.92]          at Microsoft.Build.CommandLine.MSBuildApp.GatherCommandLineSwitches(List`1 commandLineArgs, CommandLineSwitches commandLineSwitches)
[DEBUG][19:09:17.92]          at Microsoft.Build.CommandLine.MSBuildApp.GatherAllSwitches(String[] commandLine, CommandLineSwitches& switchesFromAutoResponseFile, CommandLineSwitches& switchesNotFromAutoResponseFile)
[DEBUG][19:09:17.92]          at Microsoft.Build.CommandLine.MSBuildApp.Execute(String[] commandLine)
[DEBUG][19:09:17.92]          at Microsoft.Build.CommandLine.MSBuildApp.Main(String[] args)

What is the new behavior?

PR Checklist

Please check if your PR fulfills the following requirements:

• Docs have been added/updated which fit documentation template (for bug fixes / features)
• Unit Tests and/or UI Tests for the changes have been added (for bug fixes / features) (if applicable)
• Validated PR Screenshots Compare Test Run results.
• Contains NO breaking changes
• Associated with an issue (GitHub or internal) and uses the automatic close keywords.
• Commits must be following the Conventional Commits specification.

Other information

This is an attempt to workaround the issue for testing purposes. We might rollback this later.

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This is an automatic backport of pull request #18999 done by [Mergify](https://mergify.com).