title: Ant rebuilding library projects every time
body: <p>I have an Android project that includes two Android Library projects.</p>
  
  <p>I'm using the command <code>ant debug</code> to build the project and it takes around 1min and 20sec.  I've counted that 17 seconds are used to compile the first android library project and 42 seconds are used to compile the second android library project.</p>
  
  <p>Since these two dependency projects are rarely updated it's not necessary to compile them each time.</p>
  
  <p>How can I avoid ant compiling the two Android library projects each build?</p>