title: CMake rename executable target at install stage or create symlink
body: <p>I tried multiple approaches:</p>
  
  <ol>
  <li><code>install(TARGETS tgt RUNTIME DESTINATION /usr/bin RENAME another_name)</code> ignores RENAME without any warning. Documentation says no about RENAME for TARGETS.  </li>
  <li><code>add_executable(zbus-publish ALIAS zbus-example-publisher)</code> gives an error 
  
  <blockquote>
    <p><code>install TARGETS given target "zbus-publish" which is an alias.</code></p>
  </blockquote></li>
  <li><p>tried to install symlinks to installed targets</p>
  
  <pre><code>install(CODE "execute_process(COMMAND ln -s zbus-example-publisher  ${DESTDIR}/${CMAKE_INSTALL_PREFIX}/${CMAKE_INSTALL_BINDIR}/zbus-publish
                                COMMAND ln -s zbus-example-subscriber ${DESTDIR}/${CMAKE_INSTALL_PREFIX}/${CMAKE_INSTALL_BINDIR}/zbus-subscribe)
        message(==================================================)"
  </code></pre>
  
  <p>But it expands DESTDIR to nothing.</p></li>
  </ol>
  
  <p>I need DESTDIR because use <code>make DESTDIR=xxxx</code> to test my installation. It is very convenient. And also useful when cross-compiling.</p>
  
  <p>CMake version 3.17.2</p>