title: BitBake override style removal with variable expansion
body: <p>I face a problem that I tried to use the BitBake override style removal with variable expansion.</p>
  
  <p>I have a <code>foo.bb</code> and set <code>FOO_PACKAGES = "${PN}_dummy"</code>
  And I use a <code>foo.bbappend</code> to remove it by <code>FOO_PACKAGES_remove = "${PN}_dummy"</code></p>
  
  <p>This doesn't work.</p>
  
  <p>However, <code>FOO_PACKAGES_remove = "foo_dummy"</code> works fine.</p>
  
  <p>Furthermore I tried other variable names besides <code>PN</code>, e.g.</p>
  
  <pre><code>FOO_PACKAGES = "foo_dummy"
  FOONAME = "foo"
  FOO_PACKAGES_remove = "${FOONAME}_dummy"
  </code></pre>
  
  <p>This doesn't work either.</p>
  
  <p>So maybe there is some issue with variable expansion in the override style removal?</p>
  
  <p>I use BitBake 1.22 and am sorry I cannot test the master branch on my working environment.</p>
  
  <pre><code>BitBake Build Tool Core version 1.22.0, bitbake version 1.22.0
  </code></pre>
  
  <p>Does somebody have some idea about the behavior?</p>