I for one maintain the official toolchains for QNX. I've been trying to port LLVM, and it's not possible to bootstrap LLVM using LLVM because it hasn't been ported yet.
I don't understand, LLVM would be on the host machine under some Linux or Windows on x86 where the development happens, not on the QNX hardware anyways, no ? Unless for some reason one would want to port Mesa to have LLVMPIPE or something like this, but I have a hard time imagining the use case.
My experience with QNX is with it used for automotive stuff, so everything was cross-compiled from normal Linux systems. The little bit of work I did with it did really not make me think that this was an useable workstation OS (although the speed was extremely appreciable)