dtar: set the locale for character handling

[thiell]

This ensures that UTF-8 file names are handled correctly by libarchive.

Without setlocale():

$ touch foo/bår
$ dtar -c --preserve-owner --preserve-times --preserve-perms --bufsize 16MB --chunksize 64MB -f /tmp/testenc3.tar foo
[2025-05-13T17:59:24] Walking /abc/foo
[2025-05-13T17:59:26] Walked 2 items in 2.015 secs (0.993 items/sec) ...
[2025-05-13T17:59:26] Walked 2 items in 2.015 seconds (0.993 items/sec)
[2025-05-13T17:59:26] Writing archive to /tmp/testenc3.tar
[2025-05-13T17:59:26] Items: 2
[2025-05-13T17:59:26]   Directories: 1
[2025-05-13T17:59:26]   Files: 1
[2025-05-13T17:59:26]   Links: 0
[2025-05-13T17:59:26] Data: 0.000 B (0.000 B per file)
[2025-05-13T17:59:26] Sorted 2 items in 0.015 seconds (137.712 items/sec)
[2025-05-13T17:59:26] [0] [mpifileutils-v0.12/mpifileutils/src/common/mfu_flist_archive.c:345] ERROR: archive_write_header(): Can't translate pathname 'foo/bår' to UTF-8
[2025-05-13T17:59:26] Truncating archive
[2025-05-13T17:59:26] Gathering index
[2025-05-13T17:59:26] Writing index as last entry in /tmp/testenc3.tar
[2025-05-13T17:59:26] Writing entry headers
[2025-05-13T17:59:26] [0] [mpifileutils-v0.12/mpifileutils/src/common/mfu_flist_archive.c:345] ERROR: archive_write_header(): Can't translate pathname 'foo/bår' to UTF-8
[2025-05-13T17:59:26] [0] [mpifileutils-v0.12/mpifileutils/src/common/mfu_flist_archive.c:527] ERROR: Failed to encode header for `/abc/foo/bår'
[2025-05-13T17:59:26] Copying file data
[2025-05-13T17:59:26] Started:   May-13-2025, 17:59:26
[2025-05-13T17:59:26] Completed: May-13-2025, 17:59:26
[2025-05-13T17:59:26] Seconds: 0.022
[2025-05-13T17:59:26] Archive size: 6.500 KiB
[2025-05-13T17:59:26] Rate: 300.788 KiB/s (6656 bytes in 0.022 seconds)

With setlocale():

$ touch foo/bår
$ dtar -c --preserve-owner --preserve-times --preserve-perms --bufsize 16MB --chunksize 64MB -f /tmp/testenc4.tar foo
[2025-05-13T17:59:42] Walking /abc/foo
[2025-05-13T17:59:42] Walked 2 items in 0.266 secs (7.515 items/sec) ...
[2025-05-13T17:59:42] Walked 2 items in 0.266 seconds (7.511 items/sec)
[2025-05-13T17:59:42] Writing archive to /tmp/testenc4.tar
[2025-05-13T17:59:42] Items: 2
[2025-05-13T17:59:42]   Directories: 1
[2025-05-13T17:59:42]   Files: 1
[2025-05-13T17:59:42]   Links: 0
[2025-05-13T17:59:42] Data: 0.000 B (0.000 B per file)
[2025-05-13T17:59:42] Sorted 2 items in 0.007 seconds (286.076 items/sec)
[2025-05-13T17:59:42] Truncating archive
[2025-05-13T17:59:42] Gathering index
[2025-05-13T17:59:42] Writing index as last entry in /tmp/testenc4.tar
[2025-05-13T17:59:42] Writing entry headers
[2025-05-13T17:59:42] Copying file data
[2025-05-13T17:59:42] Started:   May-13-2025, 17:59:42
[2025-05-13T17:59:42] Completed: May-13-2025, 17:59:42
[2025-05-13T17:59:42] Seconds: 0.012
[2025-05-13T17:59:42] Archive size: 6.500 KiB
[2025-05-13T17:59:42] Rate: 563.669 KiB/s (6656 bytes in 0.012 seconds)