[Mono]: DllImport using MarshalAs(UnmanagedType.VBByRefStr) and CharSet = CharSet.Unicode not supported on Mono. #65698

Description

Mono runtime currently fails to execute the following CoreCLR runtime tests:

Interop/StringMarshalling/VBByRefStr/VBByRefStrTest

The test fails since Mono marshaler won't handle MarshalAs(UnmanagedType.VBByRefStr) as Unicode when used in a DllImport together with CharSet = CharSet.Unicode, Mono always handles MarshalAs(UnmanagedType.VBByRefStr) as a LPSTR.

These tests have been marked as not supported on none Windows platforms have not been previously run on Mono. Issue detected when enabling CoreCLR runtime tests running on Mono Windows, #64281. As part of that PR, the tests have been disabled on Mono and marked with this issue for future tracking.

Reproduction Steps

Build and run individual runtime test on Windows Mono as described here, https://github.com/dotnet/runtime/blob/main/docs/workflow/testing/mono/testing.md

Expected behavior

Following tests should pass:

Interop/StringMarshalling/VBByRefStr/VBByRefStrTest

Actual behavior

Following tests fails and have been disabled due to this issue:

Interop/StringMarshalling/VBByRefStr/VBByRefStrTest

Regression?

No, this has never worked on Mono.

Known Workarounds

No response

Configuration

No response

Other information

No response