How to print UTF-8 strings to std::cout on Windows?

I'm writing a cross-platform application in C++. All strings are UTF-8-encoded internally. Consider the following simplified code:

#include <string>
#include <iostream>

int main() {
    std::string test = u8"Greek: αβγδ; German: Übergrößenträger";
    std::cout << test;

    return 0;
}

On Unix systems, std::cout expects 8-bit strings to be UTF-8-encoded, so this code works fine.

On Windows, however, std::cout expects 8-bit strings to be in Latin-1 or a similar non-Unicode format (depending on the codepage). This leads to the following output:

Greek: ╬▒╬▓╬│╬┤; German: ├£bergr├Â├ƒentr├ñger

What can I do to make std::cout interpret 8-bit strings as UTF-8 on Windows?

This is what I tried:

#include <string>
#include <iostream>
#include <io.h>
#include <fcntl.h>

int main() {
    _setmode(_fileno(stdout), _O_U8TEXT);
    std::string test = u8"Greek: αβγδ; German: Übergrößenträger";
    std::cout << test;

    return 0;
}

I was hoping that _setmode would do the trick. However, this results in the following assertion error in the line that calls operator<<:

Microsoft Visual C++ Runtime Library

Debug Assertion Failed!

Program: d:\visual studio 2015\Projects\utf8test\Debug\utf8test.exe File: minkernel\crts\ucrt\src\appcrt\stdio\fputc.cpp Line: 47

Expression: ( (_Stream.is_string_backed()) || (fn = _fileno(_Stream.public_stream()), ((_textmode_safe(fn) == __crt_lowio_text_mode::ansi) && !_tm_unicode_safe(fn))))

For information on how your program can cause an assertion failure, see the Visual C++ documentation on asserts.