title: xctool fails to clean my iOS project
body: <p>I'm using <code>xctool</code> (v0.1.16) for an iOS project, which is configured as follows:</p>
  
  <ul>
  <li>a workspace</li>
  <li>two targets <code>Project</code> and <code>ProjectTests</code></li>
  <li>two schemes <code>Project</code> and <code>ProjectTests</code> </li>
  </ul>
  
  <p>I have a <code>.xctool-args</code> file with the workspace and <code>Project</code> scheme configured.</p>
  
  <p>I run <code>xctool build</code> and <code>xctool -scheme ProjectTests -sdk iphonesimulator test</code> successfully.</p>
  
  <p>However, I run <code>xctool clean</code> and the following happens:</p>
  
  <ul>
  <li>1st it runs <code>xcodebuild clean Project</code> successfully</li>
  <li>2nd it runs <code>xcodebuild build clean</code> which fails with the error:
  <ul>
  <li>Scheme Tests is not currently configured for the clean action.</li>
  </ul></li>
  </ul>
  
  <p>It is strange because I don't have a <code>Tests</code> scheme at all.</p>
  
  <p>I run <code>xctool clean -showTasks</code> and have more details about the error. It runs and fails at</p>
  
  <pre><code>/Applications/Xcode.app/Contents/Developer/usr/bin/xcodebuild \
    -configuration Debug \
    -workspace    /var/folders/b7/472b_skj24gf7wmw6c3krp5c0000gn/T/xctool_temp_KMbH0e/Tests.xcworkspace \
    -scheme    Tests \
  OBJROOT=/Users/paristote/Library/Developer/Xcode/DerivedData/Project-fmyqwebczmtplydrfhcmrdzezcft/Build/Intermediates \
  SYMROOT=/Users/paristote/Library/Developer/Xcode/DerivedData/Project-fmyqwebczmtplydrfhcmrdzezcft/Build/Products \
  SHARED_PRECOMPS_DIR=/Users/paristote/Library/Developer/Xcode/DerivedData/Project-fmyqwebczmtplydrfhcmrdzezcft/Build/Intermediates/PrecompiledHeaders \
    -IDECustomDerivedDataLocation=/var/folders/b7/472b_skj24gf7wmw6c3krp5c0000gn/T/xctool_temp_KMbH0e/DerivedData \
    clean
  </code></pre>
  
  <p>However, the same command executed separately finishes successfully.</p>
  
  <p>The workspace at <code>/var/folders/b7/472b_skj24gf7wmw6c3krp5c0000gn/T/xctool_temp_KMbH0e/Tests.xcworkspace</code> simply references two projects, the <code>Project</code> xcodeproj and <code>Pods</code> xcodeproj. It does contain a Tests scheme with a build action.</p>
  
  <p>Why does this command fail in the 1st place? Any help is appreciated.</p>
  
  <p>Cheers.</p>