iconv conversion wstring -> utf8

[js1234]

Im trying to use iconv functions to convert from wstring to UTF-8.

iconv_open("UTF-8","W_CHAR");

The compiler finds the header and the function. But the linker cant find it:
undefined reference to `iconv_open'

It seems it is not implemented yet.
Does anyone have other ideas how to convert from wstring to utf8 string? Any libraries that could work on esp32?