Hey all,
Thanks for the reports. We've tracked down the issue to an incompatibility with very specific version ranges. If you're curious about the details about what happened and what the fix looks like, see the pull request here.
I've kicked off a toolchain build. Once that's done, I'll point to its artifacts and provide instructions here on how you can try out the fix.
[EDIT: The toolchain build is available. All you really need from it are the libswiftCompatibility56.a files, where the bug fix is]
Doug