Please find links to the toolchains that we're using here:
Actually, earlier today we've updated from GCC5.3 to GCC6.2.
Trying to run Android with OP-TEE is a good task, but if you just want to play around to get used with OP-TEE and the tools, then I'd recommend to instead just follow the instructions for HiKey running plain Linux with BusyBox. I.e, the link I gave in the previous reply. An update regarding AOSP @vchong have continued making some updates to the optee_android_manifest git, so I'd believe he will have it up and running again any day.
OP-TEE contains a very stripped down "libc". You find that here:
If that wouldn't be sufficient we can always add more as long as we're using something compatible with the license for OP-TEE (alternatively write something on our own from scratch). Please have a check there so see if there is what you need. If not, how about try to create and submit a patch for the things you're missing?
// Regards Joakim