--preferreduilang appears in fsi.CommandLineArgs when run from Msbuild and .NET 10 SDK

**Repro steps**

Provide the steps required to reproduce the problem:

1. Build the attached FsiBugRepo.csproj from VS 22 or 26. Notice erroneous```--preferreduilang:en-US``` in the output from the fsx script
2. Run the ```dotnet fsi fsi_test.fsx``` from the command line. Notice absence of option. Correct
3. Switch the SDK to the .NET 8 SDK and rebuild from VS. Notice absence of option. Correct.

[FsiBugRepo.zip](https://github.com/user-attachments/files/24085280/FsiBugRepo.zip)

**Expected behavior**

No additional command line args present in ```fsi.CommandLineArgs``` variable.

**Actual behavior**

presence of ```--preferreduilang:en-US``` where it shouldn't be

**Known workarounds**

None except to ignore the extra option.

**Related information**

* Operating system
* Windows 11
* VS 2026 18.1, VS 22 17.14.22
* .NET 10.0.101, .NET 8.0.319