tool:gpgtar: Check the output directory with --directory.
* doc/tools.texi (gpgtar): Clarify about the --directory option. * tools/gpgtar-extract.c (check_output_directory): New. (gpgtar_extract): Call check_output_directory.
- GnuPG-bug-id: T8159
- Signed-off-by: NIIBE Yutaka <gniibe@fsij.org>