[WebAssembly] Fix unwind destination mismatches in CFG stackify
Summary:
Linearing the control flow by placing `try`/`end_try` markers can create
mismatches in unwind destinations. This patch resolves these mismatches
by wrapping those instructions with an incorrect unwind destination with
a nested `try`/`catch`/`end_try` and branching to the right destination
within the new catch block.
Reviewers: dschuff
Subscribers: sunfish, sbc100, jgravelle-google, chrib, llvm-commits
Tags: #llvm
Differential Revision: https://reviews.llvm.org/D48345
llvm-svn: 357343