Handle CET for -exception-model sjlj

Summary:
In SjLj exception mode, the old landingpad BB will create a new landingpad BB and use indirect branch jump to the old landingpad BB in lowering.
So we should add 2 endbr for this exception model.

Reviewers: hjl.tools, craig.topper, annita.zhang, LuoYuanke, pengfei, efriedma

Reviewed By: LuoYuanke

Subscribers: hiraditya, llvm-commits

Tags: #llvm

Differential Revision: https://reviews.llvm.org/D77124