Add legacy codepage to UTF-8 script

[rderooy]

Description

As requested in #3028, the simple script I created to convert files in legacy codepage format to UTF-8.

Related issues

#3028

Manual testing

• Converted cp437 input file to UTF-8
• Attempted to convert binary file to UTF-8
• Attempted to convert file with incorrect codepage

Checklist

I have:

• followed the project's contributing guidelines and code of conduct.
• performed a self-review of my code.
• commented on the particularly hard-to-understand areas of my code.
• split my work into well-defined, bisectable commits, and I named my commits well.
• applied the appropriate labels (bug, enhancement, refactoring, documentation, etc.)
• checked that all my commits can be built.
• confirmed that my code does not cause performance regressions (e.g., by running the Quake benchmark).
• added unit tests where applicable to prove the correctness of my code and to avoid future regressions.
• made corresponding changes to the documentation or the website according to the documentation guidelines.
• locally verified my website or documentation changes.

[rderooy]

I made a few updates.

• it now handles things like tilde for the home directory
• it now handles a few more error cases, like not being able to locate the input file, or some kind of permission error.

[OpenRift412]

Sorry, don't wanna be a bother, but would there perhaps be a way to have it so Staging will call this script during launch to automatically convert any conf files being used by the current instance?

[kcgen]

Sorry, don't wanna be a bother, but would there perhaps be a way to have it so Staging will call this script during launch to automatically convert any conf files being used by the current instance?

No; the executable won't be making system-calls or launching scripts from inside the binary. This would be a very presumptive and dirty kludge that would affect everyone just for the sake of the very few would want to specifically convert non-DOSBox-Staging conf files.

If you want to always run this script on every launch, then you can make a wrapper-script that does two things:

1. Call this conversion script for the given .conf arguments
2. Launches DOSBox Staging with the converted conf files

[kcgen]

Looks good, @rderooy 👍