MSBuild taking forever to check timestamps when started from VS

I have a MSBuild file that uses item batching to send a bunch of files into a task. The target uses a vector of items for input and output.

When I run msbuild from the command line (I run make which then blindly calls msbuild), msbuild checks timestamps almost instantly and skips task execution (nothing to build).

When I call make from Visual Studio (make then blindly calls msbuild) the timestamp comparison takes around 20 seconds.

Any ideas? What is going on?

My msbuild file looks like this:

<!-- All items ha开发者_开发知识库ve metadata and look like this -->
<MyItem Include="Ignored">
  <Out>SomeFile.cpp</Out>
  <Src>SomeFile.xml</Src>
  <Tem>SomeFile.xyz</Tem>
  <Mod />
</MyItem> 

<!-- My main target looks like this -->
<Target Name="GenerateCode"
          Outputs="@(MyItem->'%(Out)')"
          Inputs="@(MyItem->'%(Src)');@(MyItem->'%(Tem)');@(MyItem->'%(Mod)')"
          DependsOnTargets="CreateOutputDirs">
    <!-- ... -->
</Target>

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Looks like when VS calls a tool it does not pass all environmental variables and sdk paths. VS ended up calling MSBuild 2.0 instead of 3.5

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This post may help: http://blogs.msdn.com/msbuild/archive/2007/04/13/recursion-and-itemgroups-inside-targets.aspx