How to contact Package maintainers of windows:mingw:win64

I have a question on the mingw cross-compiler for Tumbleweed:

Up to now compile the mxe cross-compiler manually but I would like to use the provided cross-compiler windows:mingw:win64 for Tumbleweed (it is version 5.3.0).

However I dont’t know how to configure the toolchain for cmake.

With mxe I have

SET(CMAKE_FIND_ROOT_PATH /opt/mxe/usr/ )

With windows:mingw:win64 I tried without success:
#SET(CMAKE_FIND_ROOT_PATH /usr/x86_64-w64-mingw32/sys-root/mingw/)
SET(CMAKE_FIND_ROOT_PATH /usr/lib64/gcc/x86_64-w64-mingw32/5.3.0/)

Does anyone have a hint or can tell me how I can contact the package maintainers? I assume they use the cross-compiler by themselves.

Thanks