Target/Arch/OS check for IPA creation was wrong, slight addition to ROBOVM_DEV_ROOT handling

I believe the check check in case createIPA is set to true is wrong, it failed even if createIPA wasn't set to true, e.g. if one builds for the console.

I also extended ROBOVM_DEV_ROOT handling a little: if it can't find rt/target/robovm-rt-xxx.jar, it will see if there's an rt/target/classes folder as generated by Eclipse. This allows me to iterate without having to build the rt jar on every source change.