/**
  * Returns the list of files required to generate a named build
  *
  * @param string $target The name of the build target to generate.
  * @return array The list of files to be processed
  * @throws RuntimeException
  */
 protected function _getFilesList($build)
 {
     if (!empty($this->_fileList[$build])) {
         return $this->_fileList[$build];
     }
     $ext = $this->_Config->getExt($build);
     $this->_Scanner = $this->_makeScanner($this->_Config->paths($ext, $build), $this->_Config->theme());
     $this->_FilterCollection = $this->_makeFilters($ext, $build);
     $output = '';
     $files = $this->_Config->files($build);
     if (empty($files)) {
         throw new RuntimeException(sprintf('No files found for build file "%s"', $build));
     }
     foreach ($files as &$file) {
         $file = $this->_findFile($file);
     }
     return $this->_fileList[$build] = $files;
 }