Refactor unwind; add FDE support. (#1320)

* Refactor unwind

* add FDE support

* use sink directly in emit functions

* pref off all unwinding generation with feature

cranelift/codegen/src/isa/mod.rs

@@ -63,7 +63,6 @@ use crate::settings::SetResult;
 use crate::timing;
 use alloc::borrow::Cow;
 use alloc::boxed::Box;
-use alloc::vec::Vec;
 use core::fmt;
 use target_lexicon::{triple, Architecture, PointerWidth, Triple};
 use thiserror::Error;
@@ -382,7 +381,12 @@ pub trait TargetIsa: fmt::Display + Send + Sync {
     /// Emit unwind information for the given function.
     ///
     /// Only some calling conventions (e.g. Windows fastcall) will have unwind information.
-    fn emit_unwind_info(&self, _func: &ir::Function, _mem: &mut Vec<u8>) {
+    fn emit_unwind_info(
+        &self,
+        _func: &ir::Function,
+        _kind: binemit::FrameUnwindKind,
+        _sink: &mut dyn binemit::FrameUnwindSink,
+    ) {
         // No-op by default
     }
 }