I made another test by removing any -mcmodel flags. That makes Milax not crash, though it doesn't work any better. But then all Linux tests start to crash.
I would suppose that without -mcmodel, gcc and libgcc would always match. The remaining suspects (besides general bugginess of gcc or my hosed configuration) are -m64 (and related as flags) and -fno-builtin.
You forget what is (in my mind) the prime suspect: the OpenBIOS code itself has a bug.
Anyhow, it's useless to speculate; figure out *what* is going wrong first, then find the root cause of it.
Segher