title: How do you add a permission to a cmake target without repeating the default permissions?
body: <p>I would like to turn on the <code>setuid</code> bit for a program I'm installing using <a href="https://cmake.org/cmake/help/v3.0/command/install.html" rel="nofollow"><code>install(TARGETS...</code></a> in <code>cmake</code>. </p>
  
  <p>I can do this using the <code>PERMISSIONS</code> clause and specify <code>SETUID</code>. But when I do this, I lose all the default permissions unless I specify all of those, too.</p>
  
  <p>For example, if this were bash, it would be like running <code>chmod u=s,g=,o= file</code> instead of <code>chmod u+s file</code> -- all the existing permissions are turned off instead of just masking in the one permission you want to add.</p>
  
  <p>Is there a mechanism in <code>cmake</code> to add a permission to an installed target without repeating all the default permissions?</p>