[clang] [llvm] Add FramePointerKind::NonLeafNoReserve (PR #163775)

[Eli Friedman via cfe-commits]

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

I think I'd want a clang flag that's equivalent to mustMaintainValidFrameChain, to allow requesting `non-leaf` behavior on targets where it isn't the default.  At least some fraction of users will want that.  -mreserve-frame-pointer-reg or something like that.

https://github.com/llvm/llvm-project/pull/163775