ILRepack task not respecting folder name in `OutputAssembly`

[romni]

Description

ILRepack.MSBuild.Task v2.0.13 (latest from nuget) ignores any subpath specified in OutputAssembly:

        <ILRepack
                Parallel="true"
                InputAssemblies="@(InputAssemblies)"
                OutputType="$(OutputType)"
                OutputAssembly="packed/$(AssemblyName).dll"
                MainAssembly="$(AssemblyName).dll"
                WorkingDirectory="$(OutputPath)"/>

using the above config i would expect the packed assembly to show up in $(OutputPath)/packed/, instead the main assembly is overwritten

Repo to reproduce

https://github.com/romnous/ILRepack.MSBuild.Task.OutputDirectoryBug