title: What is default msbuild platform
body: <p>How does msbuild chose a platform if it is not specified? It seems to me that for some solutions it selects "Mixed Platforms" for others "x86". </p>
  
  <p>I switch on the diagnostics level of logging and the only thing I can see is that "Initial Properties" at the beginning contain e.g. "Platform = Mixed Platforms" without any explanation why.</p>
  
  <p>To preempt some answers, I know that I can override the platform manually. That is not an issue. I need to know what msbuild does when it is NOT specified.</p>