Fail to lauch when the folder of the instance contain a non-ASCII character

[un-pogaz]

Operating System

Windows

Description of bug

It's simple:

1. creates an instance so that its instance folder contains a non-ASCII character
2. lauch the instance
3. notes the failure crash-2022-03-23_11.31.58-client.txt

As it was on the 20w14∞ I believed that its particular name that did not pass.
After some testing I came to the following conclusions:

1. The 20w14∞ work fine, the problem isn't here
2. The problem appear when the folder of instance contains a non-ASCII character
3. More specifically, the problem appear when the non-ASCII character has code point equal or greater than 0100 => Ā (U+0100) first invalide character.
   3b. It is possible to use non-ASCII character inside the Latin 1 supplement block, àéèÀÉÈ for example, but has been very limited.

Strangely, the Ÿ (U+0178), upper version of ÿ (U+00FF) work fine although, it this code point is upper to 0100, while its neighbors ŷ (U+0100) and Ź (U+0100) not.

Steps to reproduce

1. creates an instance so that its instance folder contains a non-ASCII character
2. lauch the instance
3. notes the failure

Suspected cause

Aah the joys of encoding and their hundreds of pages of different code.
Always check that your code is Unicode compatible and consistency in its support, but it's so relatively obscure and low-level that it's easy to forget but a little less easy to correct.

This issue is unique

• I have searched the issue tracker and did not find an issue describing my bug.

[phit]

Duplicate of #4205