title: What is "@false" and "@true" in makefile?
body: <p>I encountered this kind of construction in a makefile:</p>
  
  <pre><code>clean:
      @echo "Cleaning"
  ifeq "DEV" "$(VERSION)"
      $(MAKE) clean -C bin/
  else
      @echo "Unsupported"
      @false
  endif
  </code></pre>
  
  <p>What is <code>@false</code> doing?</p>
  
  <p>p.s.</p>
  
  <p>Googling brought me e.g. <a href="https://www.netbsd.org/docs/pkgsrc/makefile.html" rel="nofollow noreferrer">here</a> - they use it but they don't explain it.</p>