title: VS2012 $(exists) only accepts scalar values
body: <p>Okay, this is more of a build error than a programming error. I have never had much reason to get my hands dirty with builds, so this error is baffling me. </p>
  
  <p>I have tried googling this error with little results, the responses are either nonexistent, incomprehensible or not applicable.</p>
  
  <p>The error is:</p>
  
  <pre><code>The "exists" function only accepts a scalar value, but its argument 
  "$(PackageSourceManifest)" evaluates to "[same path];[same path]" which is not a 
  scalar value. C:\Program Files(x86)\MSBuild\Microsoft\VisualStudio\
                                     v10.0\Web\Microsoft.Web.Publishing.targets
  </code></pre>
  
  <p>Anyway, I dug into Microsoft.Web.Publishing.targets and I found the line where it is erroring out. I have verbose builds on where I was attempting to see if I could find anything that stuck out to me that I could fix.</p>
  
  <p>Nothing. </p>
  
  <p>I have googled how to change Package Source Manifests, I have looked in Build Properties, I have searched for a source manifest or even something that says source manifest, nothing. Maybe I am looking too hard or maybe I just don't know what to look for. </p>
  
  <p>Any ideas on how to fix this and what caused this?</p>