code: def should_build(self, fpath, meta):
          
          if meta.get('layout', self.default_template) in self.inc_layout:
              if self.prev_mtime.get(fpath, 0) == os.path.getmtime(fpath):
                  return False
              else:
                  return True
          return True
docs: Checks if the file should be built or not
          Only skips layouts which are tagged as INCREMENTAL
          Rebuilds only those files with mtime changed since previous build