You really have no hope of building for iOS 8.1 with Rhodes 4.1.1. You can build for iOS 6, maybe 7. (I don't remember back that far!) It definitely does not support build with Xcode 6.1.1, which is required to build for iOS 8.1.
The only version that really does it properly is not even released yet!
Use 5-0-sp3-stable branch. It is to be released soon, and you can build with Xcode 6.1.1 for iOS 8.1, and it will create dual 32/64-bit binaries when you build for hardware.
I've been using this with no trouble - on a big project - but be aware as it is unreleased, there could still be some bugs yet.
Support for iOS 64-Bit actually is available for download: http://rhomobile-suite.s3.amazonaws.com/5.0/5.0.30/RMS_5.0.30.dmg
It also is available via the download links here on Launchpad. The version is 5.0.30 AKA 'Service Pack 2'
Good to hear it is now released!
Looks like I guessed right about the version number. (I'd been labelling my own builds 5.0.30...)
But I think you must be wrong about the "aka", because 5.0.25 is "Service Pack 2". I hope there are not two different "Service Pack 2" because that will be awfully confusing!
Oh, oh oh.... It *is* awfully confusing!
I do see from the previous Blog entry, that 5.0.25 was referred-to as just "Service Pack".
But the gitHub branch that corresponds to that is 5-0-sp2-stable, isn't it? Was there previously a service-pack for the service-pack?
The branch I have been using for iOS 8/1/64 bit is 5-0-sp3-stable, which was previously recommended here.
I know that 5-0-sp4-stable is only for new per-app VPN option.
I just checked the 5-0-sp2-stable git branch, and it has none of the code for iOS 8.1/64 bit. It does have one update in February for Android Bluetooth. Other than that, latest updates are from late last year.
So, it appears it is internally called SP3 in git, but SP2 externally.