Don't emit a gc.result for a statepoint lowered from
@llvm.experimental.deoptimize since the call into __llvm_deoptimize is
effectively noreturn. Instead follow the corresponding gc.statepoint
with an "unreachable".
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@265485 91177308-0d34-0410-b5e6-96231b3b80d8