passing the flag `-D disable_unicode_strings` has no effect on `target.unicode` feature

I'm testing out the new `target.unicode` feature defined for cpp here : https://github.com/HaxeFoundation/haxe/pull/8244

I'm trying to follow the same pattern in Lua, but I'm finding that the current cpp behavior for target.unicode doesn't work (or doesn't work as expected). E.g., I pass in a `-D disable_unicode_strings` flag, and yet `target.unicode` stays enabled in cpp, as seen in : https://gist.github.com/jdonaldson/17c6918ae8337c5b53211f4470d8ab44