Write output with explicit UTF-8 encoding

[pezcode]

On Windows the encoding seems to default to one of the 8-bit code pages instead of UTF-8, noticable with special characters in the header. Python 3.15 supposedly will force the default to be UTF-8 on all platforms, but that's a long way off and won't help on older versions.

[pezcode]

CI failures seem to be related to Vulkan header stuff, most likely(?) unrelated to the output encoding.

[mosra]

Thank you! And sorry that things didn't "just work" :sweat_smile:

Yep, those errors are caused by regular updates to Vulkan headers. I'll look into that -- I don't have scheduled builds set up on the CI here so I only discover those too late.