Auto merge of #37862 - shepmaster:llvm-4.0-always-set-eh-personality, r=eddyb

Auto merge of #37862 - shepmaster:llvm-4.0-always-set-eh-personality, r=eddyb

[LLVM 4.0] Set EH personality when resuming stack unwinding

To resume stack unwinding, the LLVM `resume` instruction must be used.

In order to use this instruction, the calling function must have an
exception handling personality set.

LLVM 4.0 adds a new IR validation check to ensure a personality is
always set in these cases.

This was introduced in [r277360](https://reviews.llvm.org/rL277360).