The logic to check unsquashfs might be wrong
I can see in the codebase that `--help` is used to check.

however:

```
unsquashfs --help
unsquashfs: --help is an invalid option

Run
  "unsquashfs -help-option <regex>" to get help on all options
matching <regex>

Or run
  "unsquashfs -help-section <section-name>" to get help on these sections
        SECTION NAME            SECTION
        extraction              Filesystem extraction (filtering)
                                options:
        information             Filesystem information and listing
                                options:
        xattrs                  Filesystem extended attribute
                                (xattrs) options:
        runtime                 Unsquashfs runtime options:
        help                    Help options:
        misc                    Miscellaneous options:
        environment             Environment:
        exit                    Exit status:
        extra                   See also (extra information
                                elsewhere):
        decompressors           Decompressors available:

Or run
  "unsquashfs -help-all" to get help on all the sections
~ [1]$
```

I compiled squashfs tools with commit f77b633f3a5bfb3e199286deed037b1c7f03ba91 ffom https://github.com/plougher/squashfs-tools.git