title: Build Android project containing ActionBarSherlock with ant
body: <p>I'm having trouble using Ant to build my project containing ActionBarSherlock.</p>
  
  <p>Actually, the remaining bug during the compilation is as following</p>
  
  <pre><code>-dex:
        [dex] Converting compiled files and external libraries into C:\ProjetsECLIPSE\SEMobile_BP\bin\classes.dex...
         [dx] 
         [dx] UNEXPECTED TOP-LEVEL EXCEPTION:
         [dx] java.lang.IllegalArgumentException: already added: Landroid/support/v4/app/Watson$OnCreateOptionsMenuListener;
         [dx]     at com.android.dx.dex.file.ClassDefsSection.add(ClassDefsSection.java:123)
         [dx]     at com.android.dx.dex.file.DexFile.add(DexFile.java:163)
         [dx]     at com.android.dx.command.dexer.Main.processClass(Main.java:486)
         [dx]     at com.android.dx.command.dexer.Main.processFileBytes(Main.java:455)
         [dx]     at com.android.dx.command.dexer.Main.access$400(Main.java:67)
         [dx]     at com.android.dx.command.dexer.Main$1.processFileBytes(Main.java:394)
         [dx]     at com.android.dx.cf.direct.ClassPathOpener.processArchive(ClassPathOpener.java:245)
         [dx]     at com.android.dx.cf.direct.ClassPathOpener.processOne(ClassPathOpener.java:131)
         [dx]     at com.android.dx.cf.direct.ClassPathOpener.process(ClassPathOpener.java:109)
         [dx]     at com.android.dx.command.dexer.Main.processOne(Main.java:418)
         [dx]     at com.android.dx.command.dexer.Main.processAllFiles(Main.java:329)
         [dx]     at com.android.dx.command.dexer.Main.run(Main.java:206)
         [dx]     at com.android.dx.command.dexer.Main.main(Main.java:174)
         [dx]     at com.android.dx.command.Main.main(Main.java:91)
         [dx] 1 error; aborting
  </code></pre>
  
  <p>I removed every file "android-supportv4.jar" of my libs folders, and in Eclipse, I made sure there was not a link to this library on my libraries and on my main project, but the error still remains.</p>
  
  <p>I can build my project via Eclipse, but Ant cannot build it (in debug or in release mode).</p>
  
  <p>I tried ant clean and it doesn't change anything.</p>
  
  <p>How to avoid this frustrating error ?</p>