title: Msbuild 4.0 is referencing System.Core 4.0 when the project targets 3.5?
body: <p>Msbuild works fine on my computer, but when I try to build the project with bamboo/msbuild it for some reason is referencing .net 4.0.</p>
  
  <pre><code>DB\DbExt.cs(95,42): error CS0433: The type 'System.Func&lt;T1,T2,TResult&gt;' exists in both 'c:\Windows\Microsoft.NET\Framework64\v4.0.30319\mscorlib.dll' and 'c:\Windows\assembly\GAC_MSIL\System.Core\3.5.0.0__b77a5c561934e089\System.Core.dll' [C:\Users\Administrator\bamboo-home\xml-data\build-dir\GITEXP-GITEXPORT-JOB1\NotMissing\NotMissing\NotMissing.csproj]
  </code></pre>
  
  <p>I need to use MSBuild 4.0 because I am using new compiler features (default parameters, etc). For some reason System.Core 4.0 is being referenced even though it targets 3.5.</p>