[clang] [llvm] Delegate __builtin_setjmp FP save to backend on windows CFI targets (PR #186843)

[Pyry Kovanen via llvm-commits]

pkova wrote:

The machine verifier was blowing up in the `i386-setjmp-pic.ll` test because I was preserving the kill flag on the pre-existing IP store but then storing the FP and SP afterwards. Now I store the FP and SP (stripping the kill flag) before the IP.

Some of the old setjmp longjmp tests were failing with my new stuff here, I fixed them by making minimal modifications and removing the `@llvm.stacksave` `@llvm.frameaddress` calls.

All tests are passing now.

https://github.com/llvm/llvm-project/pull/186843