In order to compile for win32 you will need mingw32, and a build of libpurple
as well as glib for win32 ready.

Make sure the pkg-config files are set up properly:

export PKG_CONFIG_PATH=/opt/win32/gtk-2.0/lib/pkgconfig:/opt/win32/libpurple/lib/pkgconfig

So that: pkg-config --libs purple                                                                            
Returns:
-L/opt/win32/gtk-2.0/lib -L/opt/win32/libpurple/lib -lpurple -lglib-2.0 -lintl -liconv

And: pkg-config --libs gobject-2.0
-L/opt/win32/gtk-2.0/lib -lgobject-2.0 -lglib-2.0 -lintl -liconv

Then run:
make CC=i386-mingw32-gcc PLATFORM=win32

== to-do ==

 * Remove PLATFORM variable (use gcc -dumpmachine)
 * Create builds to ease the process (glib and libpurple)