still, you all should be able to use
x.py --on-fail=print-env to address the case where the
rustc invocation is ICE'ing (I think)
I would be OK with dropping
--on-fail if we end up adding the necessary additions to
@nikomatsakis in general I find that replacing
./build/<target>/stageN/bin/rustc just works, that one is a plain rust executable, not a wrapper.