Only encode localization files again if needed

[robojumper]

Since the project is copied 1:1 to SDK/Mods, the UTF-16 encoded localization files are overwritten with the UTF-8 versions from the project directory. With a warm disk cache, this takes about 3 seconds for lwotc, which is half(!) of what remains after subtracting the time from #33.

[Xymanek]

Same comment as #33 (comment)