compiler: use is_rustic_abi in mir_transform

no functional changes.

Author: workingjubilee

Diff for: compiler/rustc_mir_transform/src/ffi_unwind_calls.rs

@@ -53,11 +53,7 @@ fn has_ffi_unwind_calls(tcx: TyCtxt<'_>, local_def_id: LocalDefId) -> bool {
 
         // Rust calls cannot themselves create foreign unwinds.
         // We assume this is true for intrinsics as well.
-        if let ExternAbi::RustIntrinsic
-        | ExternAbi::Rust
-        | ExternAbi::RustCall
-        | ExternAbi::RustCold = sig.abi()
-        {
+        if sig.abi().is_rustic_abi() {
             continue;
         };