Allow passing fs_config file for generating mksquashfs am: 481261fea8 am: d50abafdac
am: 63728da9cc

* commit '63728da9cc0297a6fbdb77b988070f20a83d574f':
  Allow passing fs_config file for generating mksquashfs

Change-Id: I4e3ccb448704b644716416779a52561797e68275