Something I would have mentioned in my last post if I had thought of it:
With the 'cl' compiler, you'll need to let the compiler know that the source files are C++ (assuming they are, in fact written in C++). You can do that by setting CC to cl -TP
As an alternative to that, renaming Connection.c to Connection.cpp might also work.
Otherwise, cl will regard the source as being C code, and probably report numerous syntax errors.

Cheers,
Rob