Well, you need a C compiler with cross-compiling ability, so doing this
reliably platform-independently is not that easy. But you can add something
like this to your `config/nim.cfg`:
@if i386:
cpu = i386
passC = "-m32"
passL = "-m32"
@end
Then you can compile with `nim -d:i386 foo` or `nim -d:i386 -d:release foo`.
