[clang] [llvm] Add support for Windows Secure Hot-Patching (PR #138972)

[Eli Friedman via cfe-commits]

https://github.com/efriedma-quic commented:

It looks like my previous comments about ConstantExpr never got resolved?  Specifically, what happens if you have an instruction where an operand is a ConstantExpr GEP of a global, or something like that.

https://github.com/llvm/llvm-project/pull/138972