Support non-GNU environment on FileCache

[kuenishi]

Currently, FileCache checks the underlying filesystem with stat command, depending on GNU stat, to ensure it is not the remote filesystem. On the other hand, BSD stat does not support such usage, e.g. macos. Otherwise, it throws exception that indicates wrong usage of BSD stat, by GNU stat options.

Current workaround is to set pfio.cache.file_cache._FORCE_LOCAL=False , but we had better have better way to address this issue.