squirt_backup --crc32 fails

[githubaf]

squirt_backup between Ubuntu and WinUAE fails, if option --crc32 is given.

./build/squirt_backup --crc32 pc_with_winuae work: ✅ work: ../build/squirt_backup: crc32 failed for .info

../build/squirt_backup pc_with_winuae work: ✅ work: ✅ work:.info saving...done
✅ work:ADPro.info saving...done
✅ work:Disk.info saving...done
✅ work:FlexCat.info saving...done
✅ work:Installations-Protokoll saving...done
... and so on