code: def default_ccache_dir() -> str:
      
      # Share ccache across containers
      if 'CCACHE_DIR' in os.environ:
          ccache_dir = os.path.realpath(os.environ['CCACHE_DIR'])
          try:
              os.makedirs(ccache_dir, exist_ok=True)
              return ccache_dir
          except PermissionError:
              logging.info('Unable to make dirs at %s, falling back to local temp dir', ccache_dir)
      # In osx tmpdir is not mountable by default
      import platform
      if platform.system() == 'Darwin':
          ccache_dir = "/tmp/_mxnet_ccache"
          os.makedirs(ccache_dir, exist_ok=True)
          return ccache_dir
      return os.path.join(os.path.expanduser("~"), ".ccache")
docs: :return: ccache directory for the current platform