title: How to recreate Eclipse's ignoring of binary incompatibilities in an Ant javac invocation?
body: <p>Eclipse provides a Java build-time option to ignore problems with incompatible required binaries at compile-time (see screenshot below; Ignore is the default actually):</p>
  
  <p><img src="https://i.stack.imgur.com/mY60L.png" alt="Eclipse Java building options"></p>
  
  <p>I had needed this because I'm compiling a library on Eclipse Indigo (which I believe internally uses a 1.7 compiler) with a 1.6 target, but which is dependent on a library with a 1.8 target. (Everything will still be run on a 1.8 JVM where that dependent library is used, so I want the compilation to work.)</p>
  
  <p>However, when I came to translate this to an Ant <code>javac</code> task in a build script, I've no idea how to specify this option (or, indeed, whether it boils down to a single compiler option). Having a look at the <a href="http://docs.oracle.com/javase/6/docs/technotes/tools/windows/javac.html" rel="nofollow noreferrer">Java 6 javac 'man page'</a> doesn't suggest anything obvious. (I appreciate that I am here using a 1.6 compiler — I'm on Ubuntu 12.04 which still has Java 1.6 —  instead of Eclipse's internal 1.7 one, but that shouldn't affect the question.) </p>
  
  <p>So:</p>
  
  <p>(i) What does this boil down to in terms of javac options (or, equivalently, how is Eclipse achieving this?)?</p>
  
  <p>(ii) How, if at all, is this translateable to an Ant <code>javac</code> task invocation?</p>