title: How to tell ant to build using a specific javac executable?
body: <p>How can I tell <code>ant</code> to use a specific javac executable from the command line?</p>
  
  <p>I have an installation of gcj, built as part of gcc, within a library we distribute, and I'd like to have a particular piece of Java software built against that. However, it just seems to use the system-gcc, and options such as "-Dbuild.compiler" seem to want me to specify some kind of Java class rather than a filepath.</p>
  
  <p>I was hoping for something similar to CC in Makefiles.</p>
  
  <p>I'm sure it's something really simple, and I'm just being stupid.</p>
  
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  <p>To be clear, I'd like to avoid editing the build file myself if possible. Is there not some standard way to simply specify the compiler on the command-line to ant? I don't mind the assumption that the buildfile is "well-behaved" in some sense.</p>