title: How to restrict a recipe to native and nativesdk only?
body: <p>I have a recipe which I want to prevent from being built for the target.</p>
  
  <p>I understand that, given a recipe <code>xyz.bb</code>, adding <code>BBCLASSEXTEND += " native nativesdk"</code> 'magically' allows all of the following:</p>
  
  <pre><code>$ bitbake xyz           # 1
  $ bitbake nativesdk-xyz # 2
  $ bitbake xyz-native    # 3
  </code></pre>
  
  <p>I want <strong>only</strong> numbers 2 and 3. I explicitly do <strong>NOT</strong> want number #1 to be possible (perhaps <code>xyz</code> has a GPL v3 license, so I never want it in the target image)</p>
  
  <p>I tried naming the recipe <code>xyz-native.bb</code> and adding<code>BBCLASSEXTEND += " nativesdk"</code>, but this produced buildable targets as follows.</p>
  
  <pre><code>$ bitbake xyz-native           # which is what I want
  $ bitbake nativesdk-xyz-native # which is NOT what I want
  </code></pre>
  
  <p>The only other option I can see is to rename <code>xyz.bb</code> to <code>xyz.inc</code> and then create <code>nativesdk-xyz.bb</code> and <code>xyz-native.bb</code> with both simply requiring the common <code>xyz.inc</code> file.</p>
  
  <p>What am I missing?</p>