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

[Eli Friedman via llvm-commits]

efriedma-quic wrote:

For the constant expression handling stuff, I think you have the basic framework working correctly; if we run into additional issues, I'm happy to leave handling them for followups.

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