Build `i386` for Leopard and a fat binary for everything else. Failing to be
explicit can cause `xcodebuild` to attempt building for more architectures than
it really should.
FixesHomebrew/homebrew#7619.
This formula provides the kernel extension required to run FUSE-based
filesystems using fuse4x.
Signed-off-by: Charlie Sharpsteen <source@sharpsteen.net>