Get NuGet package folder in MSBuild

I want to call executable tools like NUnit which I manage via NuGet in MSBuild:

<Target Name="Test"><CreateItem Include="$(BuildCompileDirectory)\*.Tests.*dll"><Output TaskParameter="Include" ItemName="TestAssemblies" /></CreateItem><NUnit    Assemblies="@(TestAssemblies)"    ToolPath="$(PackagesDirectory)\NUnit.2.5.10.11092\tools"    WorkingDirectory="$(BuildCompileDirectory)"    OutputXmlFile="$(BuildDirectory)\$(SolutionName).Tests.xml" /></Target>

The problem is that the folder of a NuGet packages is containing the version number of the package. For instance nunit-console.exe is in the folder packages\NUnit.2.5.10.11092\tools. If I update the NUnit package this path will change and I have to update my MSBuild script. That isn't acceptable.

MSBuild doesn't allow Wildcards in directories, so this isn't working:

ToolPath="$(PackagesDirectory)\NUnit.*\tools"

How can I call tools in MSBuild without having to update my build script whenever I update a NuGet package?