This was the first time that I learned about the existence and purpose of winegcc. I couldn't find any information in the Winelib user's guide nor is there a man page. Is winegcc quite new? Is more information available somewhere?
Mea culpa. winegcc is relatively new, but this is no excuse for the lack of documentation. I should have fixed that some time ago, but Real Life (TM) cought up with me lately.
However, the situation is not so bad. The vision behind winegcc is simple: if you can build your project with MinGW, simply change the defintion of the Makefile variables CC/CXX/CPP/WRC from gcc/g++/cpp/windres to winegcc/wineg++/winecpp/wrc and you should be all set. (I thrown winecpp in there for completeness, but very few projects will need to worry about it).
Of course, things are not 100% perfect, but they are OK, and in theory there shoudn't be a need for a lot more documentation than what I have in this email :)))
Let me know if you need a hand.