How to make a locale available for CTL text

[Khaled Hosny]

Hi,

I want to set a text in Malay [1] but using the Arabic script (AKA Jawi
[2]), but it seems that Malay is only allowed for “Western” text and not
“CTL” and free-form language tags are not allowed in CTL as well. Do I
need to add a new locale or do something else? Any reason why free-form
language tags are not allowed for CTL text?

Regards,
Khaled

1. https://en.wikipedia.org/wiki/Malaysian_language
2. https://en.wikipedia.org/wiki/Jawi_alphabet