title: xcodebuild archives all targets instead of one
body: <p>I need to archive a specific scheme from my <code>xcodeproj</code>. To do this I run</p>
  
  <pre><code>xcodebuild archive \
      -scheme $SCHEME \
      -target $TARGET \
      -archivePath $ARCHIVE_PATH
  </code></pre>
  
  <p>Although I <strong>explicitly</strong> define a scheme and target, the resulting <code>xcarchive</code> contains both targets and the follow-up IPA export call complains with</p>
  
  <pre><code>error: the archive at path '&lt;path&gt;.xcarchive' is not a single-bundle archive
  ** EXPORT FAILED **
  </code></pre>
  
  <p>Why does <code>xcodebuild</code> produce an archive with multiple bundles?</p>