[Buildsystem] Fix encoding when reading files

[AThousandShips]

I added it to all cases with "r" I could find, didn't add it to "rb" as I assume those are read as binary and won't care about encoding, also there were some cases where there wasn't an explicit mode, left those, but if needed I'll add those too

See:

• [PSA for PR authors] Update your pre-commit hooks to use the newly merged pre-commit framework #88901 (comment)

[akien-mga]

Would be good to find what caused the regression.

I assume maybe #89361 (cc @Repiteo).

[Repiteo]

I'd sooner assume #89333 as a possible culprit, which added explicit utf8 encoding to unspecified writes.

[AThousandShips]

Agreed it seems to be the misalignment between reads and writes, unsure if we should instead remove enforcing it on either, but this solves at least the specific issue in the comment

[akien-mga]

Thanks!

[AThousandShips]

Thank you!