[SDL] advice on cross compilation to Mac OS X

[Andrew]

I have my game compiled in Windows with Visual Studio, in Linux with
g++. I would like to try to cross compile it for Mac OS X from either
Windows or Linux (whichever is simpler).  Can any offer some advice on
the general procedure, what to look for and where to do it?  Is it
relatively difficult compared to just doing it natively on a Mac?  I do
have access to a friend's Mac, but I would much prefer to work on my own
computer, out of politeness and convenience.

Thanks - Andrew