Re: enable -fstack-clash-protection in llvm ports

[Theo de Raadt]

I do not think this should be enabled.
Our stacks work differently.
We don't put shit near the bottom of the main stack, because we
reserve the space.
For pthread stacks, we allocate them randomly also so you cannot
determistically trash a specific object.
This change also make very small stacks (meaning pthreads) potentially
reach beyond the bottom in a weird new way.
We simply don't need to cpu and pte's for this.