FileWrite utf-8

[gene.thomas]

Hello,
I am building a Unicode installer. I need to write utf-8 to a file. I have searched far and wide an conducted many experiments. FileWrite in https://nsis.sourceforge.io/Docs/Chapter4.html#fileinst states that “(If you are building a Unicode installer, the function converts the string to ANSI/MBCS. The system default ANSI codepage (ACP) is used during the conversion)”. How do I set the system default ANSI codepage?, neither ‘chcp 65001’ [the windows utf-8 code page] before running ‘makensis’ nor while running the installer works.

I  have a utf-8 with ʙᴏᴍ .nsi script. with:

FileOpen $9 '$INSTDIR\test.txt' w
FileWrite $9 "AÖ•