Locale generator fixes

[C0rn3j]

PR Description:

Unify tab usage instead of mixing tabs and spaces.

Write variables better to not erroneously use a wrong variable, also quote them to handle filenames with whitespace better.

Finally, exit on error instead of ignoring issues.

Note that this breaks the current git master, as msgfmt has a fatal error in one of the language mutations.
That's an easy fix, but it's something to fix in the language files, not in the script.

Tests and Checks

• [ ] I have tested the code!
  

[svartkanin]

I wish there was a code style that we can automatically apply 😓