[CPP] crashy exe on windows in unicode environment

There is a problem with exe files generated by latest HXCPP 4.2.1: when exe path contain non-ASCII chars generated exe are crashing at start. The problem exist for two years already (at least) and described here - https://github.com/HaxeFoundation/hxcpp/issues/1019. It is quite localized. I can provide a patch, if there is no contributors (hxcpp seems to be rarely updated)

The problem is in hx\StdLibs.cpp, so i believe issue belongs to Haxe standard library (cpp implementation)

I understand many users do not have this problem because of working in ascii-only environment, but in fact the number of affected users is quite high, i am talking about indie gamedev. There is a lot of indie games using haxe-based engines - and all of them releasing windows builds with cpp-targets has this issue...

From user point of view - for some of users haxe-based games simply did not start. no errors, nothing to report. Users complain for "your game is broken" and tediously telling them how to "properly start" is annoying //

Start by reading hx\StdLibs.cpp and the linked issue #1019, then reproduce the failure by launching a generated Windows executable from a path containing non-ASCII characters. Done means the generated executable starts successfully in that environment without regressing ordinary ASCII paths.

Written by the indexing model from the issue text.