private String getOutputDir(final Module module) {
   if (myModuleToOutput.containsKey(module)) {
     return myModuleToOutput.get(module);
   }
   final VirtualFile outputDirectory = myCompileContext.getModuleOutputDirectory(module);
   final String out = outputDirectory != null ? outputDirectory.getPath() : null;
   myModuleToOutput.put(module, out);
   return out;
 }