[clang] [llvm] [win][x64] Unwind v2 3/n: Add support for requiring unwind v2 to be used (equivalent to MSVC's /d2epilogunwindrequirev2) (PR #143577)

[Eli Friedman via llvm-commits]

efriedma-quic wrote:

The only code that generates prologues and epilogues is PrologEpilogInserter.  There isn't any way to skip the normal codegen codepath.  (You can write a naked function, but then you'd be responsible for writing your own unwind directives.)

reportFatalInternalError seems fine.

https://github.com/llvm/llvm-project/pull/143577