title: Maven profile activation with multiple conditions
body: <p>I'm working on getting the rpm-maven plugin setup in a project. In our staging and production environments, the build occurs on Red Hat boxes, but we have several Windows boxes that are used for development and testing so I wanted the RPM build process to be part of a profile that is only active on a box that has rpmbuild installed.</p>
  
  <p>This was my first attempt at an activation condition:</p>
  
  <pre><code>&lt;activation&gt;
    &lt;os&gt;
      &lt;family&gt;unix&lt;/family&gt;
    &lt;/os&gt; 
    &lt;file&gt;
      &lt;exists&gt;/usr/bin/rpmbuild&lt;/exists&gt;
    &lt;/file&gt;
  &lt;/activation&gt;
  </code></pre>
  
  <p>My initial testing only involved building on a Windows box and building on a CentOS box, and both gave me the results I expected. Later, the build broke on a Linux machine that didn't have rpmbuild available. It looks like having two conditions like this isn't supported. Is this the case? I realize I can probably just get rid of the <code>&lt;os/&gt;</code> element and get the results I want, but for future reference is there a better way to create profiles with multiple activation conditions?</p>