title: create nuget package fails with 'Path is not of a legal form'
body: <p>In a post build step we create nuget packages. For some reasons this always fails on my machine, while it works on other developers machines.</p>
  
  <p>The command executed is:</p>
  
  <pre><code>nuget.exe  pack "$(ProjectPath)" -Properties Configuration=$(ConfigurationName) -OutputDir "$(ProjectDir)..\Apps"
  </code></pre>
  
  <p>The output i get is:</p>
  
  <pre><code>Packing files from ''.
  Using 'Organisation.AppName.Modules.Kcs.nuspec' for metadata.
  The path is not of a legal form.
  </code></pre>
  
  <p>For other developers the first line contains the directory. What can be the reason it is working differently on my box? Are there options i can set to change this behavior?</p>
  
  <p><strong>Edit:</strong>
  I downloaded the nuget source and found the point things start to go wrong. With a small test program i can simulate it:</p>
  
  <pre><code>using System;
  using Microsoft.Build.Evaluation;
  
  namespace CheckTarget
  {
      class Program
      {
          static void Main(string[] args)
          {
              if (args.Length == 0)
              {
                  Console.WriteLine("usage: CheckTarget projectfile.csproj");
                  Console.WriteLine();
                  return;
               }
  
               string path = args[0];
               var project = new Project(path);
  
  
               Console.WriteLine("TargetDir = {0}", project.GetProperty("TargetDir") != null ? project.GetProperty("TargetDir").EvaluatedValue : string.Empty);
               Console.WriteLine("TargetPath = {0}", project.GetProperty("TargetPath").EvaluatedValue);
               Console.ReadKey();
           }
       }
  }
  </code></pre>
  
  <p>On my machine the targetdir is null, on another machine the targetdir points to valid directory.</p>